295. Debunking Low Carb Science for Endurance Athletes

Summary

Some Work, All Play – Episode 295

Debunking Low Carb Science for Endurance Athletes
Hosts: David Roche & Megan Roche
Date: January 27, 2026

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Overview

In this emotionally nuanced and science-packed episode, David and Megan Roche tackle the recent social media uproar surrounding a narrative review promoting low-carb strategies for endurance athletes. The hosts dig deep into the claims behind low-carb science, dissect the flaws in recent studies, and emphasize what decades of real-world data and physiological understanding tell us about high-carb fueling for performance and health—particularly for female athletes. In between, they share personal stories, uplifting listener messages, and reflections on the role of compassion and nuance both in sport and life. The episode also covers the topic of bone density and stress fractures, highlights a moving interview with athlete Beth McKenzie, and provides a quick hit of science on recent relevant studies.

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Episode Structure & Key Segments

• [00:00] – [02:45] A somber opening and heartfelt commentary on recent events
• [03:02] – [10:00] Pizza, cheese, and why energy availability matters
• [10:00] – [14:39] Cycling breakthroughs and the value of cross-training
• [15:44] – [17:37] Bicarbonate ("bicarb") for performance & fueling sponsorships
• [17:37] – [53:38] Debunking low-carb science & the narrative review deep dive
• [54:05] – [63:41] Listener spotlight: Beth McKenzie and the complexities of anti-doping in sport
• [64:03] – [66:58] Quick takes: Alex Honnold, climbing, and the physiology of fear and stamina
• [67:08] – [84:53] Science quick-hitter: Bone density, stress fractures, and life advice
• [80:19] – [85:24] Listener celebration and closing moments

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Detailed Breakdown & Key Insights

1. Emotional and Political Context [00:00–02:45]

• David & Megan open with a somber tone, reflecting on tragic events in Minnesota and the responsibility to acknowledge truth and lead with compassion.
• They honor the memory of Alex Preddy, reading a powerful statement from his family and emphasizing their commitment to honesty and inclusion, regardless of differences among listeners.

"We want this podcast to be for everyone. You can disagree with us politically and we love you…" – David, [00:30]

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2. Carbs, Pizza, And Energy Availability [03:02–05:16]

• David and Megan riff humorously about their love for extra cheese pizza and how energy availability directly impacts training and recovery—using pizza as an accessible entry into the fueling discussion.
• Performance tip: Under-fueling (whether by insufficient carbs or cheese!) leads to poor recovery and training adaptation.

"This is a way to talk about fueling and the importance of treating your body well is sometimes you gotta go double extra cheese." – David, [04:54]

"Double extra cheese is performance cheese." – Megan, [05:02]

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3. Cross-Training Successes [06:00–14:39]

• Megan shares her breakthrough uphill treadmill workout after rest for a micro-injury—crediting both rest and vigorous cross-training (Zwift cycling) for her improvement.
• Importance of zone 2 (Z2) training and cycling as supplemental aerobic development.
• Key insight: Cross-training (primarily cycling) is increasingly important for runners in 2026, shifting the focus away from total run mileage as the primary metric.
• Physiological lesson: Higher cadence cycling is translating to improved running performance.

"2026 is the year of cross training from a training theory perspective… mileage matters, but it's not actually the thing that's driving adaptations." – David, [09:20]

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4. Bicarbonate Supplementation [15:44–16:52]

• Megan reads a listener testimonial on the performance-boosting effects of bicarbonate before a 10k race.
• Practical tip: Start with lower doses; integrate with carb-rich fueling for best results.
• Humorous aside about the DIY approach to using Morton bicarb solutions.

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5. Debunking Low-Carb Science (Main Discussion) [17:37–53:38]

A. Why This Matters (and Potential Harm)

• Low-carb messaging is pervasive and can be harmful, especially for those with disordered eating tendencies or for female athletes.
• Real-world data and performance trends in endurance sports overwhelmingly support high-carb strategies.

"We don't want to be talking about low-carb science. It's just not necessarily important… But when the message is shouted from the rooftops… we're like, all right, we should counter this." – David, [17:52]

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B. The Problem with the Research Cited

• The main study under review is a 2025 trial with 10 male triathletes, testing four conditions (varying carb intakes, often as low as 10g/hour) at only 70% VO2 max.
• Key criticisms:
  • Minimal carbohydrate dosing in the study does not reflect real-world best practice.
  • Low intensity and lack of female subjects limit relevance.
  • Results cherry-picked and interpretations biased.
• Megan highlights that even small carb amounts improve performance—but these studies don't test nor consider modern higher carb intakes (60–120g/hour) now common in elite racing.

"What happens when you start thinking about higher total numbers, like 60, 90, 120… That's a much more interesting question." – Megan, [28:20]

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C. The Narrative Review—Bias and Flawed Interpretation

• The new "narrative review" cited by low-carb advocates leans on over 600 citations but is heavily influenced by a priori bias and questionable use of AI in literature synthesis.
• Discussion of "small glucose pool" (blood glucose) versus "large glucose pool" (muscle glycogen).
• Flawed central argument: Only maintaining blood glucose is necessary, so endurance athletes should only ingest ~10g carbs/hour.
• The hosts systematically dismantle these claims:
  • Dose-response evidence is ignored or dismissed despite real-world and published results to the contrary.
  • The review is accused of dressing opinion as science by filtering data through a pre-formed narrative, rather than unbiased inquiry.

"There is zero chance that these authors were ever going to come to a different conclusion. And my question is, is that science or is that an opinion piece?" – David, [23:49]

• Notable Quote:

  "Everyone is welcome to their opinions… but if those opinions are not backed up with real world practice, a scientific article can read more like a fantasy novel." – Megan, [51:30]

D. Real-world Data and Training Theory

• The actual practice in elite endurance sport (cycling, running, etc.) is very high carbohydrate consumption, shown to drive both performance and health.
• Female athletes are particularly at risk for negative health effects with low-carb/fat-adapted approaches; endocrinological consequences are well-documented.
• Nuance: More carbs isn’t always better in every context, but high-carb fueling is necessary for high output and robust health in endurance sport.

"We love carbs because we love performance, but mostly we love carbs because we love people." – David, [51:15]

• Memorable Metaphor:

  "If zero is not very good and 10 grams is 22% improvement, we're like, well, 90 grams is obviously gonna be way more." – David, [28:28]

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6. Listener Story: Beth McKenzie and The Complexity of Anti-Doping [54:05–63:41]

• Beth, an accomplished athlete and coach, was wrongfully sanctioned due to supplement contamination and strict liability anti-doping rules. Megan and David recount Beth's resilience, compassion, and ongoing inspiration within the sport.
• Key issues:
  • The system often fails to account for nuance or intent.
  • Trail racing's casual fueling (unknown origin of aid-station food/drink) collides problematically with rigorous liability standards.
• Beth's story is both cautionary and uplifting, emphasizing community and compassion over dogma and rigid enforcement.

"All systems need space for compassion and nuance…" – David, [61:02]

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7. Pop Culture & Physiology: Alex Honnold's Skyscraper Climb [64:03–66:58]

• Megan describes watching Alex Honnold’s Taipei 101 climb with "palms sweating" and reflects on the physiology of fear and endurance.
• David muses about the risk calculus professional climbers make, their ability to compartmentalize, and whether supplemental strategies (like bicarb) could apply.
• Some fun banter about Tool (the band), climbing, and driving in the snow with their kids.

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8. Science Quick-Hitter: Bone Density and Stress Fracture Risk [67:08–77:57]

• Summary of a recent Japanese prospective study on elite female runners (21 athletes, monitored for six months; high incidence of stress fractures).
• Key findings:
  • DEXA-measured lumbar spine bone mineral density is the strongest predictor of stress fracture risk.
  • Takeaway for listeners: All who have a history of disordered eating, amenorrhea, or repeated bone injuries should get a DEXA; low bone density is not destiny.
• Listener Q&A: A young woman with low BMD and frequent injuries asked if she must give up running. Megan and David provide a deeply compassionate, science-based view—she should not lose hope, as recovery and bone health can significantly improve even after years of difficulty.
• Practical tips: More carbs, regular periods, strength training (especially load-bearing), high-dose vitamin D (if deficient), and possibly collagen for tendons.

"Every single one of them is able to work through it eventually … the body is miraculous. It is so wild what you can see when days add up to weeks, up to years." – David, [74:13]

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9. Listener Corner & Episode Wrap [80:19–85:24]

• The episode finishes with a celebration of a longtime listener earning a PhD while the podcast kept them company.
• Joyful banter about hair, nails, collagen, family, and the emotional support system sports provide through difficult times.
• The hosts share their gratitude and wish for more simple, fun episodes—but affirm the value in deep dives, even if the science feels contrarian or complex.

"We love you. Thanks for being here. If you want a simple episode, talk about Patreon. That's a place where last week we had the goofiest episode of all time." – David, [83:07]

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Notable Quotes & Moments

• "Double extra cheese is performance cheese." (Megan, [05:02])
• "Carbs seem to address all of these questions… but nothing in human physiology is simple, especially metabolism." (David, [49:10])
• "There is a boneyard of ruined careers from serious endurance athletes who have undershot carb intake." (David, [51:10])
• "If those opinions are not backed up with real world practice, a scientific article can read more like a fantasy novel. And unfortunately… without wizard fucking." (Megan, [51:30])
• "All systems need space for compassion and nuance, and I think that that's really important." (David, [61:02])
• "Every single one of them is able to work through it eventually… the body is miraculous." (David, [74:13])

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Timestamps for Key Discussion Points

• [00:00] – Somber intro, political and social context
• [04:41] – Pizza, cheese, energy availability and performance
• [06:22] – Megan's cycling and training breakthroughs
• [15:44] – Bicarbonate supplementation testimonial
• [17:37] – Why debunking low-carb claims matters
• [23:50] – Is biased science still science?
• [28:20] – Dose-dependency of carbohydrate intake
• [51:15] – Performance versus health: why carbs matter most
• [54:05] – Beth McKenzie's anti-doping story
• [64:03] – Alex Honnold's Taipei 101 climb and physiology
• [67:08] – Bone density, stress fractures, and athlete advice
• [80:19] – Listener celebration (PhD defense story) & closing feelings

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Tone and Takeaways

• The episode is equal parts rigorous, heartfelt, and irreverent—reflecting the Roches' scientific expertise, commitment to inclusivity and mental health, and signature playful banter.
• Listener takeaway:
  • Don’t be swayed by flashy headlines or narrative reviews detached from real-world practice. The best science matches what decades of athletes and coaches have learned through competition and care.
  • High-carb fueling remains foundational for performance and health.
  • Compassion and community matter more than dogma, in sport and in life.

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For more:

• Listen to bonus content and get training plans on Patreon ([53:33])
• Support athlete Beth McKenzie via Wynn Republic
• Reach out with science questions and for support—this community has your back!

Transcript

[David]

Hey, everybody. We love you all. Thank you so much for being here. You can probably tell this is a different tone than the normal Woohoo in your face that starts these episodes. But given the terrible things happening in Minnesota, that wouldn't be an authentic way to show up this week.

[Megan]

It feels hard, honestly, for us. And every week we try to show up here on the podcast with science and to make science fun and engaging and 100% authentic. And when we're being 100% authentic right now, it, honestly, it feels like existing a bit in a shit pool.

[David]

That's so true. Swimming in a ship. And everybody feels that way, right? Like, I know across political divisions, everybody's feeling that way. And we want this podcast to be for everyone. You can disagree with us politically and we love you. Like, when we say that it is not a passing sentiment that means nothing. It is inherent in who you are. And inherent in love is when you see lies being told. You stand up and say something like, tragedies are happening all the time. We get that. And we do not want this podcast to be listing tragedies. But when our government is lying about someone who by all accounts did show up with love, we think we have a responsibility to point it out and to let our listeners know that, like, we mean what we say when we say we love you.

[Megan]

And as a parent too, it seems obvious hearing the responses from Alex Preddy's parents and you know, the heartbreak that they've been through, just how hard this is, but also how amazing of a human he was. And today we want to honor that. Before Woohoo. And his parents wrote a powerful statement that I think would be helpful to read.

[David]

Yeah. And they asked people to share it. So here's the statement from his family. We are heartbroken, but also very angry. Alex was a kind hearted soul who cared deeply for his family and friends and also the American veterans whom he cared for. As an ICU nurse at the Minneapolis VA Hospital, Alex wanted to make a difference in this world. Unfortunately, he will not be with us to see his impact. I do not throw around the hero term lightly. However, his last thought and act was to protect a woman. The sickening lies told about our son by the administration are reprehensible and disgusting. Alex is clearly not holding a gun when attacked by Trump's murdering and cowardly ICE thugs. He has his phone in his right hand and his empty left hand is raised above his head while trying to protect a woman. ICE just pushed down, all while being pepper sprayed. Please get the truth out about Our son. He was a good man. Thank you.

[Megan]

He was a good man. Yeah.

[David]

So we love you. And now prepare for a little bit of a tone shift.

[Megan]

This is quite a tone shift. But we're here, you know, this is what we do weekly. And hopefully it provides you with a small dose of comfort and love in a really, really hard time. And without further ado.

[David]

Yes, thank you. I was like, yeah, you're right. And I need that comfort and love right now too. So hopefully talking about carbs will. Will help people.

[Megan]

Carbs are the true comfort.

[David]

Yeah. We love you no matter what. Woohoo. Welcome to the Some Work All Play podcast. We are so happy to be with you today.

[Megan]

Happy Tuesday. It's Tuesday and it's feeling like an extra cheese Tuesday.

[David]

Oh shit. It's feeling like an extra cheese every day.

[Megan]

I was gonna say that's really every day of the week. This has been our new jam.

[David]

Okay. Okay. It's always been my jam. You just don't know because I order the pizza and I always click extra cheese. And you're like, they put a lot of cheese on this. And I'm like, ah, no.

[Megan]

Like, this is odd. Every place gives us so much cheese. But now I about it.

[David]

Okay, okay, so there's a difference, right? There's the American pizza joints, which is where we go sometimes. There's a place called Abos here in Boulder that gives you a lot of cheese at baseline, that's extra cheese. Warranted still. But then there's this other genre of pizza place which is like your fancier spot that just gives you some cheese.

[Megan]

And you don't like those places.

[David]

No, they're the worst.

[Megan]

Whenever I'm like thinking about selecting a dinner place and I find this like nice Italian pizza place, you're like, oh, hell no. Yeah, I want the American cheese factories.

[David]

I click on Google and just see the images and I'm like, if that cheese ain't. Ain't dripping, I ain't coming.

[Megan]

Same.

[David]

Exactly. And so what I learned is we went to a place that's not fancy. Fancy, but it's a fancy enough up in the mountains. And you don't just order extra cheese once. If you say extra cheese once, they just upgrade it to like a normal amount of cheese. You gotta say extra, extra cheese.

[Megan]

You gotta be like, give me the cheese. That every single bit of cheese that you have in this establishment, we want it all. We want a boatload of cheese.

[David]

How much cheese you want? All of it.

[Megan]

Of it.

[David]

So I'm very proud of that because I feel like that's really important from an energy availability perspective because sometimes these places, my guess is if you did like, you know, calorie reading on the pizza that doesn't have cheese, you're not getting that much unless you eat like four of them.

[Megan]

I've actually noticed that I haven't had great training days. Sometimes after we go to that place high up in the mountains because I don't think they put enough cheese on their pizza. And I wake up sometimes in the middle of the night hungry, and that's just not good for next day training.

[David]

Boom. So this is a way to talk about fueling and the importance of treating your body well is sometimes you gotta go double extra cheese.

[Megan]

Double extra cheese is performance cheese. Performance cheese.

[David]

Okay, we have the best episode for you today. We're gonna start by talking about Megan's biking, a fun story from last week. Then a big discussion debunking low carb science. Important after the extra cheese discussion.

[Megan]

I'm kind of strangely excited for this. Are you? We don't usually like debunking science. We usually like uplifting science. Yes, but you know what? Something about. I'm just like feeling it.

[David]

You're stinky. I can smell your hormones raging.

[Megan]

Yeah, my testosterone is flowing.

[David]

Then we' to talk about Beth McKenzie's beautiful episode on the free trail podcast. We love her so much. Then Alex Honnold free solo on Netflix. A lot of thoughts there.

[Megan]

I watched it. You really didn't.

[David]

No.

[Megan]

No, you chickened out.

[David]

Too nervous. Too nervous. Then a perspective study on DEXA scans and stress fractures. Maybe a study on low intensity training adaptations, plus a Q and A on the weirdness of AI training Z2 ranges, heart rate recovery, and more.

[Megan]

I'm excited for this one. We got a lot of good science, debunking science, and some good listener questions too.

[David]

Yeah, the low carb study was a social media just revelation. Last week it was all over everybody's account and we got sent it maybe a hundred times. And that's always an example of. All right, we need to dig in here. So we're gonna talk about that in a sec. Before we do, though, last week you did an amazing uphill treadmill workout. We've talked about those before. 10 by 5 minutes you were flowing. And I think it was kind of a breakthrough, right?

[Megan]

Actually kind of building back last podcast episode, we talked about the fact that I took five days off to let a little foot like micro injury he and didn't feel it, but came back to have my strongest workout I've maybe ever had, um, which part of me was like, why? How did that happen? That's strange. That came out of nowhere. But I think some of it might have just been from giving my body the space to like, rest and send it on the bike.

[David]

You know, the non linearity of training adaptations, it's always difficult to know, right? It's so easy to be, well, whatever I did within the last five days caused this breakthrough when in reality, you know, it's years of bricks stacking up. And so for you, though, historically, biking has always played a role. So you did this 10 by 5 minute, and then the next day you're going to go down and do your zwift route, which is like 50 miles with solid amount of climbing. And you were mentioning to me, oh, well, what should I do all this? You're like, oh, I'm just going to go down and hold over 200 watts. And I'm like, no, don't fucking do that. That is way too hard. That is not our goal the day after a workout.

[Megan]

Well, I was motivated because you took on my time on this route on YouTube in your heat suit and you beat. And I was like, I need to go back for. I need to like, stake my family claim and go back and do this. And so I was very extrinsically motivated on this one.

[David]

I thankfully, as coach, was able to step in and say, no, no, Megan, not a good dog, bad dog. Um, and then the next morning, of course, you can imagine where this is going. I come downstairs 45 minutes into Megan's ride, and that power is high as hell. And her average watts are way over 200. And I'm like, you bitch.

[Megan]

To continue the dog metaphor, I was like, I'm here for it. Cause I'm crushing bitches. Yeah.

[David]

So it was remarkable. I mean, you averaged over 200 watts for this session, all in zone two. Heart rate for the most part, at the end, with your average heart rate.

[Megan]

Well, part of the family game was that we had to keep heart rate under 160 and cadence above 90. And I do think that, like, higher cadence has helped me on the bike. And I think that was part of the reason that the power felt more natural. And maybe that's some of the reason I felt good on the uphill treadmill this week too.

[David]

Yeah. And so I think it just points out the importance of cross training in how you do it. Exactly. It's like you're not getting on the bike to just chill. You're getting on the bike to push.

[Megan]

A Bit, you know, actually to obliterate your time. But that being said, like, I'll be real, like, you know, those are good power numbers for a runner who's cycling. I would get absolutely obliterated in the women's, like, esports, Zwift world, or even if I showed up to the Tour, I'd probably end up in a ditch on the side of the road because of bike handling.

[David]

Well, the second part's true. The first part not actually. Um, I posted a video of you doing this and there was just a little bit of hint of your numbers. Like, I try not to talk too much about that. We're talking about it here because it's training theory based. And I got messages from professional female cyclists that were like, holy shit, I hate her.

[Megan]

Any from Kate Courtney? She's the only, she's the only female cyclist. I'm like, I only want her opinion.

[David]

That's how I feel about basically everything. I want to know what Kate thinks.

[Megan]

She's my hero. I love her. But no, to be real, I would get obliterated in women's peloton.

[David]

But you've built up so much over time. And, you know, for those that are cross training or working it in more, I think 2026 is the year of cross training from a training theory perspective. I think we're going to see more and more athletes have success using a lot of cycling and then talking about it in a way that brings the science of cross training, which has always been bubbling beneath the surface, into the forefront where we learned, okay, mileage was always a red herring that mileage matters, but it's not actually the thing that's driving adaptations. You only need enough mileage to have all of your aerobic volume go into a running economy pot. And that's what you're doing. And it's remarkable that you've built that power without doing bike workouts. You just do a lot of Z2.

[Megan]

I enjoy Z2. It's so fun to like go downstairs. And this is the thing. Like, I think Zwift and gravel biking have opened up this, like, aerobic development for me because before when I was using cross training, that wasn't primarily bike focused. It's like, how long are you going to go to the gym and be on an elliptical for? And people watch in the gym like, you know, doing that for longer than 90 minutes is incredibly mind numbing and feet numbing. Like, everything in your body, like goes numb because it's not fun.

[David]

I mean, you would do it.

[Megan]

I would do it. And I have done it.

[David]

I would not do it by any means. And when people do it, I really think it's remarkable. But the tools we have now are so fun and so interesting. Like, I'm having the same experience in that I'm coming back from, you know, this torn plantar and still haven't been able to run. But I finally graduated from my heat suit bikes. I'm able to put out a little bit more power, and it's transformative. In fact, this weekend you did. You're like, I'm going to film you when you do your next interval. Because I was doing on the Uphills to Chase jerseys, which points out how fun Zwift can be in indoor cycling. And so you filmed. You brought Leo in. And then my dad came to the Original Coach Roach.

[Megan]

3 Generation of Roaches in our mountain pain cave, which also happens to be our bedroom, which is like a good pain cave vibe.

[David]

I thought you were going to say three generations of roaches also happens to be an infestation. But dad was standing right beside me, and it was so meaningful because, you know, he was a bike racer when I was growing up, and when he was in his late 30s, he would take us all around the country to races like Super Weak and things like that. And he was by no means a professional. He just did this for the love of the game and, you know, to have him beside me. And I distinctly remember I was like, way above VO2 max, pushing a ton of watts. And dad said we used to fuel this off of ham and cheese sandwiches.

[Megan]

Can you imagine that? Your mom was talking that she used to give him, like, a little parcel out in the ride, and he would just open it up. It was his ham and cheese sandwich. And that was legitimately how. How they fueled. Okay. But the funny thing is, your dad looks a lot like an older version of Scott Jurek. And if you're watching the video that we took and you posted on Strava, it's like you got like the, like the Scott jerk future standing there watching you put out 500 watts. And it's a great video.

[David]

And then at the end, you know, he's just like, I was good, but I was never that good. And it was so meaningful and fun to see, especially, you know, as I'm coming back and remembering that while running and racing is really cool, just really fun to push yourself and learn new things. And in this process, I'm learning a lot. And we've talked about this is going to be a very cool science experiment because on one hand, I have the heat suit and how that's evolved. And already coming back. I'm seeing power numbers I've never seen as the heat suit comes off.

[Megan]

Well, you're seeing power numbers you've never seen at 8,500ft. You're doing this up in our mountain pain cave. And at one point, you know, you got the jersey that you wanted and you're like, look at my time. And like, yeah, you're at 8,500ft, too. And you're like, oh, I forgot. I'm like, you forgot, you little hemoglobin bitch.

[David]

I do have hemoglobin privilege. In fact, we took Ollie, our one year old, to his one year appointment and he got his first hemoglobin reading. And I was nervous. I had butterflies. I was doing those little nervous poops because this isn't destiny. But I was like, did he get my genetics? Which were passed down from my mom, who has abnormally high hemoglobin, to a single, single gene variant of hemochromatosis. And sure enough, he tested off the charts.

[Megan]

He tested at 14, which is like coming for me. So the pediatric reference range usually ends at 12. Depends on where you look, but that's high.

[David]

So I was pumped about that. And that's cool. And then so coming back from heat suit, I'm seeing that. Which probably is a hemoglobin mass increase and maybe just a training stress increase. And I was doing that to protect my foot. But secondary is that because of the injury, I've had to do lower torque cycling. And so I've been riding with a higher cadence. In fact, Yesterday I averaged 97 cadence. And we've talked on the podcast before that I'm a grinder. I like to push really big gears at really low cadences. And that could be one reason that it hasn't always translated as well to running in the winter season, but it does in summer when I ride in higher cadences out there outdoors. So we're getting a very cool experiment that I can't wait to see the outcome of. It's like, when I come back to running, how will this translate compared to expectations? Because if so, it might allow us to evolve our training theory framework. And if so, we'll. We'll keep you updated.

[Megan]

Okay. High canon cycling is my new jam. Yeah, I'm all about it. You know, I was always like, kind of high, like 85 to your 65.

[David]

Which is so low when I'm going hard.

[Megan]

Yeah, yeah, but that's like, that is low. You're, you're pushing some watts there at low cadence. And for me, like being above 90 now makes a difference. And I think it's translating to running well.

[David]

I mean, it's so inspiring to see you on the bike. And we're having fun family rivalries now.

[Megan]

And heated family rivalries.

[David]

Oh, a heated rivalry.

[Megan]

Uh huh.

[David]

Yeah.

[Megan]

We still need to get on that train.

[David]

We need to watch the show perhaps, but it's just been. Yeah, it's been fun. So I can't wait to see how your cycling translates to the top level of ultra running this year. And I have some theories, but we'll report back when we know them.

[Megan]

Oh, look at you. You're over there cooking up some things. Like what does this involve?

[David]

I can't wait. Okay, so before we get on to the low carb science article, a quick promo for the feed. Go to the feed.com SL swap. Swap. If you're a first time customer there, you get 40% off your first order. And if you're a returning customer, you get ten dollars off every hundred dollars spent.

[Megan]

Okay. I've been recently on a big roll of enervit gels. They are so tasty. And this is citrus flavor. So I always do cola because I'm like, I want a shot of 100 milligrams of caffeine often before I train. Like, it makes me feel good. But I've realized that the citrus flavor as I'm doing high carb is just tasty and I look, look like forward to taking it.

[David]

Enervit gels are bonkers. Good. That's the best ad to do is get yourself some enervit gels. You'll love it. You know, we love the science and sport beta fuel gels, but they're almost always sold out now, which is pretty cool. I think everybody's come around to them. Enervit will be the next thing that sells out, so get on that train.

[Megan]

Okay. Citrus versus mango.

[David]

I don't know the difference. Yeah, yeah, they're all vaguely of the same family.

[Megan]

Like I'm slurfing them, not really tasting them anyways. That's such a man answer. It is. It's like I give a haircut. I'm like, which do you like better? You're like, I don't really know.

[David]

No, I see. They all look beautiful.

[Megan]

See, I love all my fruit.

[David]

Slipping up all the juices. Um, and then actually, final thing is a message from a listener. Holy bicarb. What is this? Magic. I took it for A workout last week and felt amazing. But today was the true test. 10k race in frigid conditions, but felt like I was flying. Fourth overall, female. Not my usual race result. And felt so strong and smooth the whole time. Thanks again for your advice.

[Megan]

That's so exciting. It's such an uplifting feeling when you take bicarbonate and you're like, this just hurts different. Yeah, in the sense that, like, it hurts a lot less, but to me, there's, like, almost this more intrinsic level of motivation when I take bicarb.

[David]

Yeah. It accesses a part of my brain that makes zero sense. So you can find bicarb on the feed. The Morton version is our favorite. As always, don't tell anyone we told you this, but order the biggest dose, and then you can cut it in half. Or if you're a smaller athlete, even into thirds when you first start out, when you run out of the substrate that you put it in, you can just use a hydrogel and I shouldn't have said any of that.

[Megan]

Look at you stirring the pie. I'm just.

[David]

I'm just feeling it today.

[Megan]

You know, our episode is like debunking low carb. And you're like, I just wanna. Want to. Just want to stir the pot before I really stir the pot of a.

[David]

Lot of cheese macaroni in a pot. That's some what s bicarb. Okay, so let's get on to the low carb science article. And maybe a prelude before we get to it is, you know, we don't want to do this. We don't want to be talking about low carb science. It's just not necessarily important. I think everybody that's listening to this probably knows, but there is a consideration we have about overall health and how these messages can filter into the community at large. So when the message is shouted from the rooftops and basically the people promoting it are saying, you are myopic and stupid for disagreeing with this, we're like, all right, we should counter this. Because if we don't, these messages might infiltrate in just very small ways. People's thinking in a way that affects their health.

[Megan]

And I think from what I've seen over time, too, is that athletes that have disordered eating or eating disorders, which is a very large population in the endurance world, I feel like sometimes there's a bias to want to, like, validate those feelings and to grab onto studies like this and be like, look, this is, you know, low carb is about health. This is supporting my health, when in reality, it's supporting things that are actually quite dangerous to health, especially for female athletes. And so I agree. I think this is important. Yeah.

[David]

And performance wise, these questions have been answered and we will talk about that throughout. We don't want to solely say, hey, look at the real world, because in my opinion, that's dispositive. But that isn't the only thing. Right. Like, there could be little things that we're missing or, you know, blind spots we have that are important to address. We're thinking about health mainly when we say this. It's like we want to make sure people understand that this isn't a performance thing so that the health consequences aren't felt later because, you know, from a performance end, like, who cares? Who cares who wins a race at the end of the day, even if someone's a professional? Like, there's bigger things in life.

[Megan]

Well, I kind of do when it comes to our heated family rivalry. And I think this gets at the point is like, for me to take on your numbers in the heat suit, I'm like, I have to take a gel every 20 minutes. And this truly does matter for performance. In fact, if I was like, really trying to go for it and was above Z2, I might even do more than that was the realization that I had. But I think my bias just comes down to the idea of scoreboard. It's like, look at all of these performances that we're having right now in the real world fueled by carbs, almost every one of them, to the point that it's hard to compete at lower carb levels.

[David]

It's impossible to compete at lower carb levels unless you're just way more talented or have way better training.

[Megan]

And in some ways that's a problem because, you know, these cyclists don't have to train so much because they can, because they're healthier.

[David]

And it's weird because, you know, I think for most athletes, it's all about health at the top end of cycling. And this probably goes for cross country skiing and things, though I don't follow that sport as closely. You're seeing a level of burnout that we haven't seen in the past because athletes are basically pushing hard. Kind of like Megan on the bike, where you did this high wattage Z2 effort with tons of carbs and recovered really well. But they can do that almost every day. Whereas in the past you were so much more limited by, you know, how the body could, like, absorb the training without as much carbs. And also your pharmacy. So, yeah, really relevant and on that note, Zach Bitter has been a really vocal critic of this particular study and that's fascinating because he is maybe the most low carb known, ultra runner and high performance athlete. He had the 100 mile world record for a while and he has since gone on to have more carbs. He views things in a nuanced way. He's not saying it in like all high carb all the time, but what he wrote in response to this on Twitter, is this, like it or not, a high degree of competitive pressure? And here is in all caps, is your daddy, is your daddy. I like this, not all caps. You could be the most published person, have a degree from every major institution, and you would still be outpaced by a high degree of competitive pressure in answering any question about performance optimization.

[Megan]

And that's actually why I love exercise physiology, is because there's almost like two fields. There's what's happening within research and within studies, and then there's what's happening within the broader athletic context of performance. And both of those, there's arrows going between both of those in all ways. And it's kind of fun to have that like, system of checks and balances on one another.

[David]

Yeah. And that's why the best practitioners always have their understanding of both worlds. Right. And I think the people that wrote this article are really firmly stuck in their own academic bubble, which is very small. Right. This is an echo chamber they are in and they mean well, I think. But on the other hand, there are tons of scientists that operate in both. Right. We're not just talking about coaches, we're talking about people that work in the real world. And the people that work in the real world have way better data. Data, it's way more scientific because they are working in such complex ways. And so every athlete out there knows how this works, especially professional athletes. You do little interventions, you notice how your body feels, and over time you make adjustments, things evolve. You're not just starting like, okay, high carb is objectively the best thing ever, I need to do it. You're doing little things, you feel better. Kind of like the athlete that wrote about bicarb and is now going to be a bicarb proponent. But not everyone will be. So the competitive pressure is very similar to evolutionary pressure where over time some the best genes for surviving will win out. And similarly, that's what we're seeing in athletics. And that's why the real world is a little bit relevant as we're starting to talk about, you know, just this little academic sliver and in the academic.

[Megan]

Sliver, you know, I have a lot of challenges with how this narrative review was structured, particularly around one of the studies that many of these authors were part of. That being said, though, I have been impressed with how they've engaged in the discourse of the conversation.

[David]

And now we're going to be diplomatic.

[Megan]

No, we're going to throw them a bone. But you know what, it's going to be like, like a five gram of carb bone. Like we're saving the good ones for us.

[David]

Okay, okay, okay.

[Megan]

But I do think, like, you know, to give the researchers props, like, you know, they very strongly have their viewpoints, but you know, online they've actually been not necessarily like, I wouldn't call it like open minded in terms of thinking about, okay, what happens if we take in 60 grams or 90 grams or 120 grams of carbs, but at least very kind in the conversation of understanding that not everyone is going to have the same viewpoint as.

[David]

They've always been nice to me online.

[Megan]

Like I've got a bias. Whenever anyone's nice to me, I'm all about it.

[David]

We're still doing a whole segment debunking their narrative review. We like them. I mean, and maybe, you know, obviously this causes harm in many ways and that's a problem. And also, you know, I don't know these authors personally. They might have opinions that cause harm in other places just because of the way this is being pitched. It's being pitched in such a way that ignores, you know, the obvious nuance and is clearly trying to sell something with science. And that is the most dangerous type of science because that is not science. Science asks unbiased questions without knowing the answer in advance. And maybe that's the place to start is what we're looking at today is a big narrative review. We're not going to get into it quite yet, but what it essentially does is takes 600 plus citations and does it in this backfilled, ex post facto way to answer a biased conclusion they already had. There is zero chance that these authors were ever going to come to a different conclusion. And my question is, is that science or is that an opinion piece?

[Megan]

My actually other question too was how much of this was AI driven? You look at 600 of these citations, which, you know, kudos to a human if they went through and did that by hand. But literally as you go through and read the paper, they're also all written out in numbers. So it's like you have this sentence and then you have like 45 numbers of each of the citations that support them. It's like we're reading a lot of numbers here, but it does.

[David]

We should go back to being diplomatic for a second that we don't know that.

[Megan]

We don't know that. But I mean, I think it's an important question now about, you know, narrative reviews in particular. In particular, like, I think AI is changing the landscape of narrative reviews for science because it's like AI could functionally do this, whereas systematic reviews and meta analysis, which is where you're actually involving data that could be replicated, that to me is a different category and it is accepted like that within the scientific community as a different category of rigor. And so, like, a narrative review is tricky because you can do a lot of your own narrativizing and it's very easy to pull citations from any which direction.

[David]

Well, yeah, and if you know the conclusion you want in advance, you can go to ChatGPT deep research or whatever and say, hey, generate this for me. It'll think for a couple hours and deliver something that might look strikingly like this. And so let's start with the study that they did in 2025. Because the nature of a narrative review is it has so many points being made, so much is being thrown at the wall, and you can't really debunk that unless you're going to sit down and spend three weeks wasting your time on this type of thing.

[Megan]

Actually, the way they structured it was by having 16 points of evidence and using that as grounding points for this very, very long narrative review. And you wrote this in your Patreon description of it. But as I went down, I was like, increasingly starting to get, like, brain aneurysm. I'm like, oh, my lordy. And it's actually challenging because I feel like in the way that they structured it, there's oftentimes very interesting science or like a sentence where I'm like, I totally agree with that. And I'm like, wow, I found something I agree with. And the next sentence, I'm like, holy shit balls. Where did that, like, hypothesis come from?

[David]

Yeah, and the first study we'll look at gets to that point. I called it in Patreon, the duck, duck, goose approach to science, where you'll have, oh, that's an interesting point that might be correct. Oh, that's an interesting point that might be correct. Oh, what the fuck? That is so wrong. And, you know, it clouds the narrative in a way that we see very specifically in this study that we talked about last Year. But very briefly, this is used as the basis for a lot of the conclusions that are to come and also points out some of the inadequacies of the underlying thesis and where the bias comes out. So the study took 10 male triathletes and had them do four different conditions consisting of two time to exhaustion tests in each condition at 70% of VO2 max. Here are the four conditions. So, low carb adaptation in life, people that did low carb, carb plus a placebo where they didn't take in any carbs during the 70% of VO2 max time to exhaustion tests. Then low carb adaptation in life plus carbs during training, which was 10 grams per hour.

[Megan]

And they didn't do anything beyond that. In terms of higher carb groups.

[David]

Yes. Um, and then normal carb adaptation in life plus placebo, I. E. No carbs. And then normal carb adaptation in life plus carbs, 10 grams per hour. And then in between the time to exhaustion tests, they did 50 grams of maltodextrin. So some carbs. So the problems here are so freaking obvious. It's like you're testing what you say is carb intake and you're doing 10 grams per hour because they're looking at getting at hypoglycemia, essentially, which we're gonna talk about in a minute. Um, but you are not testing anything about carb intake. When you're doing that, you are solely looking at low carb. Uh, there is no differentiation between the groups, really, when you're talking 10 grams.

[Megan]

It's also relevant too, that they tested at 70% of VO2 max, which is a relatively low effort. You can see where maybe they're thinking like, okay, we're avoiding these higher intensity efforts and the findings that happen there. And what they found was that the low carb and normal carb groups perform similarly in the placebo condition, which is.

[David]

Relevant because that means that the low carb adaptation group, the people doing low carb in life, don't even get benefits when you're restricting carbs entirely.

[Megan]

How depressing is that? You're restricting carbs and you don't even get better. It's like, oh, my goodness, that has to be sad. But here's the finding was that both groups improved similarly up to 22% with 10 grams of carbs per hour on board. And that, to me, is interesting because it's like, okay, groups are improving this much with 10 grams of carbs an hour. What happens when you start thinking about higher total numbers, like 60, 91 20. Like we've seen in recent relevant literature. And I, that was, to me, I was like, oh, well, this is actually a study that might even be showing the benefits of carbs.

[David]

Yeah, well, the problem is they would argue, okay, this doesn't show dose response. Right. Because they didn't test it. Um, there were they. For us, if zero is not very good and 10 grams is 22%, we're like, well, 90 grams is obviously gonna be way more.

[Megan]

What happens when you extrapolate that out?

[David]

But for some reason they think, no, actually all that means is that 10 grams gets you all the benefit and more doesn't. And that's obviously wrong. And so here are some quotes from that study because not to delve into the science. There are other issues with the science there, but more to show how bias can come into science where their design there is fucking cool school. It's not about that. It's not about the study design. It's not about that they're doing anything wrong. It's the conclusions they reach from it are grounded in bias.

[Megan]

And I think, you know, I agree, 100. Like, the science was well done and well executed. And when you start looking at how they're interpreting this findings, you're like, whoa.

[David]

And it should make the hair stand up on your neck. When you think about a narrative review, which is all interpretation of science. So here are some quotes. Non metabolic factors must become an increasingly important cause of fatigue at this exercise intensity when the exercise is duration exceeds 2 to 3 hours, even in those who continue to ingest carbs at high rates.

[Megan]

This is the one that blew my mind because they're not even studying athletes testing carbs, taking in carbs or high rates. So I'm like, where is that Conclusion Coming from?

[David]

10 grams an hour, extremely low rates. Uh, you're clearly trying to push a narrative there. Next one. The importance of this finding is that, as discussed subsequently, it questions the logic of advising athletes to ingest carbs at very high rates during prolonged exercise.

[Megan]

Where is that logic coming from?

[David]

No, it doesn't like. It clearly does not. Uh, and then the final one here. This suggests that ingesting carbs at much higher rates may not produce additional benefits. Considering the physiological limits of the small glucose bowl, which we'll talk about in a second, that can saturate quickly. However, such an assumption requires additional testing to determine if even greater levels of carbs would translate it to greater performance.

[Megan]

Outcomes and additional testing. I'm like, wow, let's think about every recent national champion, world champion, anyone doing long endurance events. And I feel like we got a lot of testing right there.

[David]

Yeah, you have the real world testing that is off the charts. And then you have have also tons of studies coming out when they do come out on this subject that show a dose response relationship with carbs to the point that the questions are not being asked in studies anymore because they have been answered. We're not testing oh 0 vs 10 grams vs 90 grams because it'd be a waste of everyone's time. And maybe we need to go back and do that just so that these conversations can stop and we stop getting podcasts and all of this, you know, bullshit that that can infiltrate just to get back there. And I mean it's almost such an obvious answer that I think it's not being addressed that much.

[Megan]

In fact, one of our favorite studies of last year was a study that looked at 60, 90 and 120 grams of carbs. Cuz that's a much more interesting question is what happens as you start to push into the realm of higher and higher carb.

[David]

Yes. And so that brings us to the new narrative review which uses the conclusions from that study. Bronze it out with 600 plus citations as you're told. If you disagree with anything about this on social media and it is called called Carbohydrate Ingestion on Exercise Metabolism and Physical Performance.

[Megan]

I like how you read that because you really emphasize the fact that there's really not a verb in that title.

[David]

Yeah, and I don't want to get on this because I understand this is a mistake I would make.

[Megan]

Sometimes I don't use verbs. Verbs are overrated sometimes.

[David]

I've also released podcast episodes with titles that don't make sense.

[Megan]

Okay, that's different than a narrative review title.

[David]

I don't know. I give everyone compassion for everything, but especially that this obviously carbohydrate ingestion impacts would make sense, but it is missing a verb that is somewhat concerning. Uh, and so the core argument of this paper is this quote which builds off the past study. The data reviewed herein present the novel interpretation that nutritional strategies to maximize performance during prolonged exercise should be geared to maintaining the small glucose pool during exercise rather than filling or overfilling the large glucose pool before exercise. The present evidence indicates that this can be achieved by ingesting relatively small amounts, I.e 10 grams per hour of carbs during exercise.

[Megan]

I think it'd be helpful to break down what are the small and the large glucose pools. And the small glucose pool is often, and this is like simplified it's actually complicated, thought of as blood glucose, whereas the large glucose pool is often thought of stored glycogen primarily within muscle.

[David]

Exactly. And we don't want to delve too much into the exact definitions there because the liver has a complicated role that can mix it up. But in reality, they're mostly just talking about maintaining blood glucose. Avoiding hypoglycemia is the actual enemy. Like, that's the thing you're looking to do when you're fueling with carbs. Not everything you've heard the glycogen, storing it in muscle fibers and things like that. So what comes next? After this initial thesis is long and it is quite convoluted, there's like 16.

[Megan]

Evidence points and it's very, it's just, just.

[David]

It's hard because of the duck, duck, goose style where we don't disagree with everything. In fact, if you go sentence by sentence, we agree with most of it. It's much like before, where when the bias comes out, it comes out so egregiously that you're like, I don't even know where to start. And I think that that's the biggest obstacle that's happening with people refuting this study generally is you can say, oh, look at the real world. And the researchers will say, well, the real world is just missing things. And they'll say, well, actually, look at our 600 plus citations. And my response is, all right, we will, but I mean, no one has time for that bullshit. And you know, when you're starting to say, like, blatantly biased things, the only way to refute that is essentially by saying, well, no, of course not. Like, yeah, we don't have to go back to first principles and make these arguments. So I think the best way to do this is to focus on those key findings that you mentioned and see what's interesting. Essentially, like, read some quotes from them to let them use their own words and just briefly kind of point out our what, what are you talking about? Moments and then zoom out from there.

[Megan]

At the end, which should be kind of fun. And I think this actually provides some background of science. Like, I think in understanding these points, you can also understand, you know, where we're coming from of like, oh, there are potential benefits here even for how we think about fatigue resistance in the brain and, you know, thinking about what happens to the body as we go longer and longer in distance.

[David]

Yeah, and they make interesting points. You know, not all of it needs to be thrown out. Like, carbs are nuanced. Maybe that's the biggest point of all is we're not saying, take as many carbs in as you can all the time. We're saying when you're going real hard and going real long, you need to jack up that carb intake. And then generally, carbs are good for health. Um, and the nuance can sometimes be lost in these conversations, so we'll try to keep that at the forefront. All right. Do you want me to go through and read some of the quotes we pulled? And then we can just do brief responses to them?

[Megan]

Let's read some of them. It's funny, as I was going through and reading these, I don't know, I was like, am I low carb or am I just having a hard time? Sometimes I would have to go back and, like, read each sentence, like, four or five times, because I was like, what is happening here? And I don't know if it was, like, the writing style or my brain getting tripped up on the facts, but I think some of that nuance and some of the scientific complexity could be lost by reading it. And so, like, I think let's chunk it up, but do it gradually.

[David]

Okay, well, maybe what we can do is we'll read them, and if they don't work, we'll edit out a few.

[Megan]

I like that.

[David]

Yeah.

[Megan]

Yeah.

[David]

Just because we don't want any of our listeners getting aneurysms. Like Megan almost did.

[Megan]

Well, I was like. At the time, I was like, you know when you're reading, like, a complicated fantasy novel and it's taking you a second to, like, get into the world and, like, get with it? It was like, that experience for me. I was like, my brain is having a hard time coming around to these sentences. And I don't usually experience that in science. I experience that, like, in other places.

[David]

So you're talking about when the wizards aren't even fucking yet.

[Megan]

Oh, no, the wizards. I was like, I hadn't gotten there yet. And I was like, do I keep going? I really want to get to the wizards fucking. But I got to prevail through all of this. That's my number one reason to read.

[David]

Okay, so first one here. The mechanism of depletion of the skeletal muscle large glucose pool causes that. It causes fatigue. Remains hypothetical. But this. And then dot, dot, dot. This is the point that to focus on. But this is implausible. Since a developing quote, energy crisis must produce skeletal muscle ATP depletion, leading ultimately to muscle rigor, not whole body fatigue. And then we can keep going there. But, like, what muscle rigor Very similar to what you might know as rigor mortis. That isn't how the body works. Yes, the brain is connected with fatigue. Fatigue is not just a glycogen problem. Glycogen is one element of several that go into it. But this type of argument is fully nonsensical on its face, and it's the very basis of what they're saying.

[Megan]

And yes, and I think this is where sometimes there's interesting points that I'm like, yes, we need more research on how the brain interfaces with, with fatigue and how, and some of our theory is actually is that high when you're thinking about like high carb fueling, that it actually powers the brain to keep going and to keep the body going during these long efforts when fatigue resistance is starting to become a factor.

[David]

Yeah, and just the nervous system is so complex. But let's not allow the complexity cloud the basic facts. And I think that as a core fundamental tenet of their argument, undermines it right at the start. Next one. 80% of studies that reported a clear benefit on exercise performance of carb ingestion before or during exercise also found that blood glucose concentrations fell during exercise in the control or placebo group. This is important since few if any of the studies were actively studying a falling blood glucose concentration as an important factor causing exercise fatigue.

[Megan]

Well, I think this is one of those points that I'm like, well, why would we study that? That doesn't make any sense.

[David]

Blood glucose goes down when you exercise without carbs. That's just obvious. And what I said on Patreon, which had a very big breakdown of this, it's less nuanced and a little bit angrier, was it hasn't been tested because real world experience indicates that it would be like testing whether a space launch would be fueled by, should be fueled by 90% rocket fuel, since all we need to do is get off the ground, ignoring the fact that we also need to get to space. Basically, yes, blood glucose drops, but that is not the thing that's driving it. And just because we're not studying that directly, it's like, you know, do we want to go test a space shuttle without any, you know, with, with humans on board without any fuel? It's like, no, there's no need to.

[Megan]

Do that to be unethical. Exactly, exactly.

[David]

And I mean, as a lot of true low carb studies, you're starting to venture into that area, which is why like the 10 male triathletes are almost always like 45 year olds, you know, like you're not. I don't think you could give this ethically to a 20 year old 2 year old woman.

[Megan]

Yeah, I hope they're paying them well. Yeah, exactly.

[David]

Uh, next up, increasing the amount of carbon gested during exercise increases the rate of exogenous carb oxidation. This is maybe the cor tenet of a lot of the low carb arguments. According to the novel replacement theory, this additional source of obligatory carb carbs should produce an easily detectable dose dependent increase in exercise performance, I. E. More carbs, better performance. However, studies of progressively higher rates of carb ingestion during prolonged exercise fail to show serial dose dependent improvements in exercise performance.

[Megan]

This one is confusing to me because this is exactly the study that we were talking about earlier in this conversation of the dose of was dependent study on 60, 90 and 120 grams of.

[David]

Carbs an hour found 2.6% running economy improvement between 60 and 1 20. And you know, we have our misgivings about that study too. We're not saying that's dogma. We could probably do a deep dive on some of the science there. But that's every study. Um, you know, the, the difference is like when you test it in the real world, you're seeing it. And not only it's not only last year's study, there were a number of studies done by Itor Verier Bay, who now works for Salomon. But in 2020 it where he was testing 60, 90 and 120 with his research team on mountain runners and there was a dose respondent dose dependent response not just on performance, but on perceived exertion and muscle damage. So when we test this, we do see it, it's just difficult to test and it's not being done that often. Next up. Muscle glycogen is not spared during prolonged exercise as would be expected if the large glucose pool, I. E. Skeletal glycogen is the cardinal driver of exercise performance performance. Instead, the rate of muscle glycogen used during exercise is set by the muscle glycogen concentration at the start of exercise. Paradoxically, high rates of carb ingestion during exercise increase muscle glycogenolysis.

[Megan]

Well, I think that last sentence to me is one of the coolest parts of human physiology is that our metabolic system is so flexible that by consuming more carbs we burn more carbs. And I feel like that's actually like to me that's a good thing. Whereas these authors are positing that's it's bad thing. Yeah.

[David]

And Maybe the hardest part of this for me from just like a loving human physiology sort of way, is we are taking one of the most wild parts of human physiology where for millions of years we have adapted to essentially be able to burn so much fat. It is so incredible and it's one of the things that sets humans apart as these endurance creatures. But taking those to so such extremes that it's almost saying, well this biohacking approach is the right one. And that's where the real world is so relevant and the perils of bias become so apparent. It's is if the fat adapt adaptation approach, which is what they're trying to argue for, worked at all, we'd see it in the real world because there's so much competitive pressure and we don't see it. And in fact when anyone tries it, they get fucked across, across everything. Because the same evolutionary principles that allow humans to do this also down regulate other parts of human physiology, like the endocrine system that we talk about all the time, particularly for female athletes. So you're creating the situation where we're like, look at this amazing thing humans can do and hey, go fuck yourself up trying to pursue it.

[Megan]

And our evolutionary system has evolved to do that in resource poor environments, but only to do that for short periods of time. What happens if you sustain that and do these long distance ultra feats and it's like the body just gets wrecked. And that's why we're talking about this is because we've unfortunately seen the downfalls of that again and again.

[David]

Yeah, and high volume endurance training does most of this. That's why there's some nuance. Right. Like, like you shouldn't be doing 120 grams of carbs per hour if you're running 20 miles per week. Like it just doesn't work like that because then you do start to shift how your metabolism works and maybe you know, the evolution can be used against you. Uh, but otherwise maybe the most magical part of endurance training is you get these adaptations while fueling your body. And that might be a place where the researchers actually don't understand that they miss elite training theory fully because they're not in the real world to understand that an athlete like me could go out without carbs and run six minute pace. Well, not now because my foot's f. But usually for a really long time doing all of these high fat oxidation rate things that they say are impossible for carb athletes because most of those adaptations just come from training generally and from being healthy.

[Megan]

Like I would argue that it's actually really hard to have good fat oxidation in states of endocrine disruption. And the two of those, to me, it's like, you know, when you sustain that over a long period of time, I think you're just ruining your fat adaptation, paradoxically.

[David]

Yeah. And that leads to the next question. Quote, here's from them. This is because high rates of carb ingestion or infusion during exercise reduce rates of fat oxidation. This would explain the increased rates of muscle glycan genolysis.

[Megan]

That's a kryptonite phonics on that one.

[David]

We. We've done multiple takes of me saying that with high rates of carb ingestion or infusion during exercise, in effect, muscle glycogen determines its rate of use during exercise by setting the rate at which the major alternate fuel factor, fat, is oxidized. And here is where training theory is relevant. The authors are confusing aerobic inefficiency, I. E. Not training properly with metabolic inflexibility. Um, first, we are not in a race or in life looking at whoever oxidizes the most fat wins. That's not the way it works. Um, fat is less efficient from, you know, an ATP perspective. So fat oxidation is great, but you don't want to just push the numbers up to biohacking levels. But second, if you train properly, you can work across metabolic, you know, flexible ranges. And the problem is when athletes don't train, they're just gonna be burning carbs right away because they need more aerobic training. This is kind of the core of training theory. And I think because they're not practitioners and they're not working with elite athletes, they kind of just miss it, and they're like, all right, well, we're gonna have to hack the system because we can't get over 10 miles a week or whatever.

[Megan]

And I think it's because also a lot of their studies are grounded around 70% VO2 max. And the nature of these longer ultras now is that you're push the start. And this is a very different story. Like, we're not going out and, you know, having a soul journey out there and, you know, primarily relying on fat oxidation. It's like, no, the pace you're running out. You know, athletes now at western states are running up the escarpment fast at the start.

[David]

But even if they were, even if you're going, like, really low intensity, carbs make that better. Um, you're burning a. A plenty of carbs at very low intensities. If you want to be and being more efficient. And so, you know, I mean, how many listeners of this podcast have just started incorporating some carbs in their low intensity long runs and all of a sudden feel like totally different humans are adapting better, are happier, and are having better health outcomes? It's probably off the charts, right? And so, you know, real world experience starts to become relevant here. But even their scientific argument, on its face, it just misses how the body works in complex systems. And their interpretation of studies at the first end is wrong. Their interpretation of human physiology is correct, but then reaches into biased places. And then finally, the way that they holistically view this system is so clouded in belief in their low carb approach that they totally put aside the actual experience of humans that are operating outside the lab. But even in the lab lab, you would totally find something different than they're.

[Megan]

Saying, well, can you imagine going to world pro riders? Which I feel like is where we derive a lot of our science from, is happening in the pro peloton and cycling because those teams have so much funding, there's so much science going in. And can you imagine going to pro peloton riders and being like, okay, today and for the next month and for the next year, we're going to fuel your training at 10 grams of carbs per hour. I imagine everyone would quit. They'd be like, we're not doing this anymore. Like, that feels terrible.

[David]

There, there's actually these conversations happening on social media right now, which is so funny because there are researchers who work with these professional teams that are kind enough to, you know, respond on social media. And so, like us, they're getting tagged a hundred times in this study that says that their life's work is wrong. And unlike us, they actually do are doing the studies on this particular topic. And one of the guys responses who works with all these professional cycling teams is like, like, okay, we're gonna do this and see what happens. And then the researchers respond to this guy and they respond kindly, but they kind of respond in a way. It's like you are talking to the science goat that works in this field. Like, why are you talking to him as if he doesn't understand what he's, what he's doing here? And thus it just creates this really clouded water where it's just, it makes people confused. And yes, I think people within the biased zone of it will be really prone to, to, you know, just totally adopting the biohacking approach. But even if you're not in the biased zone, I think we can't see this over and over again and think, oh, well, the science. Someone will think, oh, well, the science says we should be doing some of this. And it's like, no, actually it doesn't. This is what bias says.

[Megan]

And I think the other reason this is so tricky too is that so many of these studies are talking about male athletes only. And it's like, well, what happens if you try this experiment in female athletes? It is extra poor. Like, you know, I think female athletes endocrine systems often have less margin of error when it comes to thinking about low carb approaches. And we've seen that in studies. We've seen that replicated again and again. And this actually becomes a dangerous conversation. You know, it's dangerous for male athletes, but it's especially dangerous for female athletes.

[David]

Absolutely. And would it even be ethical to run some of these experiments on female athletes?

[Megan]

Not with the current literature we have. And again, maybe there's, you know, maybe this is. We'll mark this right now. This is 2026. This is the era of high carb. That is the bias that we're existing and living in. And, you know, perhaps if there's strong evidence, good studies, you know, strong hypotheses that come out, we'll have our minds opened and be being flexible. But like, I don't really anticipate that coming.

[David]

Yeah. And these aren't strong hypotheses.

[Megan]

No, exactly. Yes.

[David]

And I actually that's an important thing before we conclude this, is that this is 2026 and it is not as simple as pushing carbs as high as you can forever. And blood glucose and hypoglycemia probably do play a really interesting role here in ways that we don't understand. And the brain's role and nervous system role in fat. Yes. So fascinating. Carbs seem to address all of these questions. That's why it's being used so much. But usually the way these conversations work is some, you know, new thing comes along, it's overdone. And then within the real world, we kind of find the healthy medium. And I do think the carb conversation can risk being overdone. Like, even people take my story. Like my story is being used a lot to refute these authors online mind. It's like, well, that's actually a misrepresentation of my story. Yes. At Leadville, I do this wild amount of carb intake.

[Megan]

You're not doing that all the time with the training.

[David]

Yeah, not at all. And in fact, I have pretty nuanced views on it that I've written about on Patreon in great detail. And so, you know, it is understanding that it's complicated. But nothing in human physiology is simple, especially when it involves metabolism, which has evolved solely for our survivability in resource poor and sporadic environments, which is not 2026.

[Megan]

And I think that's some of the coolest parts of human physiology is our ability to be flexible and to use multiple different types of fuel sources and training at the same time. It's like you can train hard carb and also train your fat oxidation at high levels of training. And guess what? Like, you know, if you're able to train at higher volumes because of higher carbs, you're also probably training your fat oxidation more.

[David]

Boom.

[Megan]

Boom.

[David]

Okay, and let's finish up with the conclusion from the article because it really underscores how we feel. Megan and I went back and forth forth writing this multiple times to just make sure we could land a plane correctly in a situation that is difficult for us because we would much prefer to just be the most uplifting people possible on this podcast.

[Megan]

And there was a point as you're writing this that was kind of banging my head and against the wall. I'm like, why are we spending so much time on this? It's like we know the science, we know this. And I think that gets to the conclusion of this.

[David]

So here it is. And that's why we're writing an article we don't want to write write about a narrative review we don't want to read.

[Megan]

And 600 citations of listed over and over again. And I was like, stop.

[David]

The real world performance benefits are clear for anyone who has traveled this path. But at the end of the day, who cares? It's just performance. The low carb believers can get left behind and that's okay by us. The reason we are writing about this relates to health. The carb conversation is nuanced. It's not about taking in as many carbs as you can all the time. And their arguments point out legitimate discussions about how to balance fueling in training and life life. But their arguments also infiltrate the broader discussion of nutrition. And anyone who works in this field sees what can happen on the other side. There is a boneyard of ruined careers from serious endurance athletes who have undershot carb intake. The negative mental and physical health outcomes from carb restriction take this out of the academic realm and into much more serious places. We love carbs because we love performance, but mostly we love carbs because we love people and we want to see athletes be able to shine their Light lights as brightly as possible.

[Megan]

And I think this last paragraph that you actually just omitted is important too. Too long. Don't read. They called their opinion piece a narrative review. Everyone is welcome to their opinions and to argue on behalf of their opinions, but if those opinions are not backed up with real world practice, a scientific article can read more like a fantasy novel.

[David]

Yeah.

[Megan]

And unfortunately, this is a fantasy novel without wizard fucking. Yeah, yeah, I read it all. I was like, where did, where did they go?

[David]

I didn't read every single word.

[Megan]

I did. I almost put my head through the ceiling.

[David]

Okay, let's move on. Maybe the final thing before we finish that is just. We're also presenting our opinion mixed with the science.

[Megan]

Oh, we are heavily biased.

[David]

Yeah. Want to acknowledge that as we talked about on the year end review. Go back and listen to the Countdown episode if you haven't, because that really delves in to the simple version of the scientific argument. And today we got into the maybe more complicated one.

[Megan]

We got into a lot of weeds there.

[David]

Yeah.

[Megan]

Was that okay?

[David]

I think it's great to be serious. I think, I think the only way to talk about this sort of thing is to get in the weeds because otherwise you're debating on terms that do not move the conversation forward. Because two sides can just say, oh, well, you know, we're just over here saying real world and scoreboard thermodynamics. And they're over there saying, you know, no, actually fat oxidation and whatever. And you're not actually meeting where the argument is happening, which is within the paper itself. And so, you know, I think I haven't seen any debunking yet. And so let's get to the actual debunking, not just to the, you know, dunking. Like, I think that's the thing. Debunking versus dunking. It's very easy to dunk. It's harder to debunk. And so hopefully that's a good role.

[Megan]

That's a great statement.

[David]

Boom.

[Megan]

I know it's like, let's debunk in the weeds together. But I think also we want to like, you know, this is friendly debunking too. This is not dunking. And I think that's an important distinction is like, everyone is entitled to their own opinions. And I think having separate opinions in a field actually in some ways moves the field forward because, well, maybe, I don't know, maybe I just said like four hours of my Sunday reading about low carb science, but it made me better in the sense of like thinking about these points and thinking about the science and you know, it challenged me in a way that I think is important.

[David]

Competition is good because, you know, through that you can learn what wins out. And so that's also goes with science. With science.

[Megan]

I love competing with athletes at 10 grams of carbs per hour. I'll see you at the finish line.

[David]

Let's go on. Before we do that quick promo for patreon, go to patreon.com swap swp you get the full article there, which is really spicy. Then also tons of training plans. We're talking talking dozens for every single goal, including the very top level beginner athletes. Everything else, heart rate zones starting at $10 a month, 177 bonus episodes. You get so much there.

[Megan]

We're working on right now putting together a return to run plan for injuries, which has been fun and thinking about like, okay, coming back from a six week injury, a 12 week injury, even things like coming back from a long layoff, potentially postpartum. And it's been fun to do that.

[David]

Yeah. So. Patreon.com swapsoap now let's talk about some news. First up is the most beautiful podcast episode on the free trail podcast featuring Beth McKenzie, who you coach, who's been in golden ticket position at trail races at what, 44 years old, 45 year.

[Megan]

Old mom of two and co founder of Wynn Republic. So she is out there busy, she's grinding and she showed up with bravery and courage. Like I've had a lot of phone calls with Beth and I could tell in her voice just how much like courage it took to do this interview. And at the same time, Dylan Bowman showed up with his like, you know, typical compassion. And I feel like the two of them together, it was just such a good vibe.

[David]

Yeah, that episode made me a better person because it was two people meeting in such a beautiful and complicated place. And so let's do some background on Beth and our relationship with her before we get into the exact story. Just to briefly tell it. I knew Beth in the Internet back in like 2008. So I was in New York City writing my dinky little blog.

[Megan]

What was it called again?

[David]

Oh man. Beauty and Change.

[Megan]

No. Beauty and Change. But you had a blog before then that was just like my duathlon blog. Beauty and Change is beautiful. Your title is really.

[David]

Oh no. I mean it's all cringe and I would hate if it came up. I honestly we should take that part out because I don't want people going and finding it on the Internet. I think I mostly deleted it but you can find everything. And she was writing blogs as well at that time and she was getting into running and later getting into triathlon, later became a pro triathlete. But my first impression of her was just someone that supported this lonely kid in New York City who was making bad questionable jokes from his dorm room room and didn't have a community. And she was so kind to me in ways that the world will never see, but demonstrated parts of her character that I knew I would always stand behind that person, even if I never really crossed paths with them. But our paths did end up crossing after Beth went through a winding road which led her to being a professional triathlete, having these breakthrough performances. And then in her post race drug sample at an Ironman triathlon, it was contaminated with a supplement called or a substance called Ostrine. And in the podcast she goes into great detail about how exactly this happened. The lawsuit, the successful lawsuit that came later, but how it still totally changed her life trajectory forever.

[Megan]

And oh my gosh, it's devastating. I mean I've heard that story, I've gone back and looked at the document. She has a substack about this and to me it's like to think about, about the hardship that she's gone through sport to have this two year sanction, which is a long time at the same time as there was another triathlete that also had Ostrin in her urine, found it within the salt tabs that she was taking and so only had a six month suspension. But this was at a time in which Ostrine was coming out as contamination in many different products. It was just a different context in terms of safe sports for sport products and how we're thinking about with contamination. And it went on to be such a struggle for Beth and to see her face that, I mean when she lines up at a start line, she faces that like, you know, in terms of the way it's talked about, the criticism. And she probably has to think about this on a daily basis.

[David]

She was so compassionate on the podcast too because she said, yeah, some people always think I'm a cheater. And she gave them love. Which I thought was so amazing because like if you're accused of something you didn't do and your life gets upended in a negative way because of it, it. Yet dumbasses online are, you know, saying bad things about you for a decade plus as you're just trying to live your life. You know, it really just shows her character that she would do that. And you know, for me it's like I saw what she was like behind the scenes and yeah, you can never know anybody's practice. But even when I heard about this in 2016, before I knew the complication of the story, I was like, this is bullshit. Like, you just, you feel that about someone and yes, I would have stick up for it. But then you hear the facts that she lays out on the podcast cast, which is done beautifully and in her substack, and essentially what ended up happening is, you know, you can't be sure of the exact source, but essentially on race day she's taking these salt pills from Carbo Pro. Um, later on, steroids were found to be at these factories in the. The same ones that she was found.

[Megan]

To have via contamination. Yeah.

[David]

Um, yet she still gets a two year ban even as they accept her explanation. And to this day, you know, she has to go to these races and one, she gets drug tested. I can't imagine how traumatic that is when you learn not to trust the system. And we've talked about that on, you know, this podcast that like the complications of it, that the system is so important even as, you know, it's much more complicated than people make it out to be, especially the dumb keyboard warriors. But on the other hand, she does these races. She miraculously gets golden tickets.

[Megan]

She's gotten two golden tickets at 44, 45, which is mind blowing.

[David]

And then can't go to western sports states because western states has a policy where if you've ever had this, you can't race. And I'm frustrated by that because I'm like, look, it's. You're not allowing for the nuance of intent. Yes, I totally understand and maybe support that. If someone does an intent, if it's deemed intentional, then you can have consequences that are up to the governing body. So, you know, western states. Sure. But if it is not, not intentional or in this case due to someone else's criminal act, like, why are you doing this to someone? You're doing it to someone because you're just trying to signal that you're serious about a topic and to just get the keyboard warriors off your back. It's like, and maybe this is going too far, but hearing Beth's story, I'm like, she should be at the Western states chart line if she wants to be.

[Megan]

Well, thinking about it like she's a 45 year old mom of two and to her, like, to what that signifies to the community in terms of inspiration of someone out there doing that to like see yourself represented in someone who is towing the line at a hundred miles in a professional, competitive way. It's like, holy shit. Like, she needs to be on the starting line. And I agree. You know, and I think the company.

[David]

If she wants to be. I don't. I don't really know that. You probably just.

[Megan]

This is the thing is, you know, as Beth was going through this process with the Western States board, which I also was a part of the board at the time, she was going through this, and I no longer am, just because it's like, you know, we have two kids, it's been busy. Like, I can't imagine how Beth does all that she does, but I think we would have used our platform more to be like, hey, Beth needs to be at Western States. The thing is, like, Beth doesn't want that. Yeah.

[David]

She doesn't want us to, like, go crazy.

[Megan]

She doesn't want us to advocate on her behalf because she's like, you know, this is my story. This is like, you know, what I've had to carry with me. And, you know, she's just not the type of person that wants us to carry it. But it's like, man, I would carry anything for Beth. Like, she's just the best person. And I feel that so deeply. But I think for me, it's one is the Western States conversation is relevant. And I think the board probably should revisit that. That conversation, because it's like there are so many nuanced cases, as Beth shows. And I think by having that role, it discredits the nuance associated with a broken system. And that's challenging.

[David]

All systems need space for compassion and nuance, and I think that that's really important.

[Megan]

And then I think my second point on this is that it shows the challenges of strict liability within trail running at its present moment. So drug testing is a strict liability instance and circumstance. And it makes me think about, like, she's talking about Triathlon back in 2016, when there were products on course that weren't even certified safe for sport, that she couldn't even get her hands on those for testing after the fact that she's receiving this notification six and a half weeks after her drug test. And then she's trying to go back through and, like, figure out everything that she took. But I feel like trail running right now, when we think about the strict liability nature of it, like, trail runners are just running through aid stations, giving their bottle to someone, having it handed back to them, and it's like. Like, that is so scary. And as we hear best story it makes me think about the idea that, like, we hold athletes right now at such strict liability, yet none of our practices, our practices within trail racing is like, you know, this, like, haphazard backyard sort of situation, which is beautiful in its own way, but it's hard to hold the two of those in tandem.

[David]

Absolutely. It's such a difficult thing. And, you know, maybe the biggest conclusion is just Beth MacKenzie's the best.

[Megan]

She's the best. Yeah.

[David]

Call her Buy Wynn Republic Gear to support her.

[Megan]

Oh, yeah. She created a company with her husband, Luke McKenzie, and they running gear, bike gear, triathlon gear. And I love different stuff.

[David]

Such cool stuff.

[Megan]

My pink. My cute pink jersey.

[David]

They work with the feet a lot, which is nice for us and just generally such a cool person. And at the end of the podcast, I bawled my eyes out listening to her tribute to you, Megan, and just how you've stood behind her. She wrote this post on Substack where she asked to include a letter from her coach. And she said to you that she was going to make it, you know, anonymous, like, from the coach. And you said, put my name on it. And that, to me is the coolest thing. And it's why I love you so much, is that behind the scenes, when nobody's watching, you're such a compassionate, you know, real person. And honestly, so similar to what I saw of Beth in 2008. And so I'm so happy you two got to meet and team up.

[Megan]

Beth is just the best. And listen to that podcast because it will come out. But also, she, in a beautiful way, has also rebuilt her life. Two kids, a business. She's coming in, and despite these daily challenges, is still going for it. And to me, that's so inspiring. It's like, how do you think about rebuilding from basically the bottom up? And she had to do that. And she's done it in a way that is just so typical Beth.

[David]

She also does trail races in super shoes.

[Megan]

What a piece.

[David]

That's my main thing. Yes, you are my queen. Don't you do them in Alpha flies sometimes, too?

[Megan]

Yeah.

[David]

Remarkable.

[Megan]

I can't remember if it was Terraware or Ultra Trail Australia, but she did one of those in Alpha Flies.

[David]

Absolutely the coolest thing I've heard. Okay, next thing on News. Last one is Alex Honnold's Skyscraper live attempt where he climbed Taipei 101. We watched it, and it was one of the weirdest experiences where I don't know exactly what the, like, motivation of Netflix was, but as I started to watch, I was like, so freaked out that I had to go into another room.

[Megan]

You left. I understand. Actually, I was reflecting on it and I was like, my palms were sweaty as I was watching it.

[David]

Knees were knee off.

[Megan]

Yeah.

[David]

Cut you off. You know what I was going to say?

[Megan]

Pulling the M and M. Yeah.

[David]

Mom's spaghetti. You get the idea.

[Megan]

Mom's spaghetti with extra cheese.

[David]

Yeah.

[Megan]

But as I was watching it, I was like, you know, I don't even know if I'd want to. To be standing on the 101. The 101st floor. 100amonth. 101st floor of Taipei. 101.

[David]

Like indoors.

[Megan]

Indoors. That's how much I don't like heights.

[David]

Yeah. It's such a cool thing to see. But after it was done, I saw him doing free solo on El Capitan again. And the moves were so much harder in the free solo movie that I'm like, this might have just felt like, you know, going up stairs to him.

[Megan]

It probably did.

[David]

Which maybe points out the whole idea of free soloing to him generally as we talked about him on the podcast, it's like the, you know, risk, reward calculus of going up the stairs to him and doing this are almost identical. Probably because he's so good. He's worked so hard at what he does and yeah, just really cool to see. Also, there, there was something called dragons where he had to do this move where he lifted up his leg. I only could watch this after the fact, and every single time to this day, I'm still pooping myself a little bit.

[Megan]

They're ten different dragons.

[David]

Yeah. What a guy. Like, I, I, I can't help but think back to when we interviewed him and he started asking us about running. Dude, if he dedicated himself to running from the beginning, what an athlete he would have been.

[Megan]

He'd be so good. Do you think he had bicarb for this event? Ah, so this is like a pretty big endurance feat. He actually said. I don't know if he was just saying this for the camera or, like, if he was actually feeling it, but like, three quarters of the way up, he's like, gee, my arms are tired. And I was like, he just needed to add a little bit of suspense to this whole equation. But as I was thinking, like, you know that, like, pumped out feeling that you get climbing. I feel like bicarb would help that a ton.

[David]

True.

[Megan]

Yeah.

[David]

Maybe that's the next way wave.

[Megan]

It also make you a little jittery, so I feel like you'd have to dose it low. But I sometimes doing strength Training after having done a workout with bicarb on board, I'm like, this is a free strength training day.

[David]

I should be very curious to know from the weightlifting world if bicarb's used.

[Megan]

I think bicarb is probably used more and more.

[David]

Yeah, maybe, maybe. I'm not sure the mechanism there, but.

[Megan]

I mean, for a long. I think it took him like an hour and a half. Plus that would be. Bicarb would help a ton.

[David]

What if they're taking Gnomeo?

[Megan]

Yeah, I could see him on the sprouts.

[David]

Not now, because it's all sold out. After we talked about it last week. Sorry about that.

[Megan]

Well, I loved. He was listening to tools.

[David]

Yeah, that's tool. I feel like you would call them metal, maybe. I think that's metal kind of. Um, but I like that that's actually a vibe when you're climbing, which you, I would assume is like peaceful and relaxing, especially when you don't have a rope. He's out there just jamming the fuck out.

[Megan]

Yeah.

[David]

What a guy.

[Megan]

What a guy. It's inspiring. I was driving down. We were driving down Boulder Canyon yesterday in the snow. It was like nasty driving conditions and. And Ollie was screaming in the backseat and Leah was playing paw patrol and I just was visualizing Alex Honnold as I was driving. And he would just block all this out and think about tools.

[David]

Meanwhile, I can't even drive in those moments because I'm too scared.

[Megan]

You see one snowflake and you're like.

[David]

No, not at all. Okay, do you want to get on the question answer or do the quick hitter science?

[Megan]

Let's do the quick hitter science. Yeah.

[David]

Okay. It's great.

[Megan]

This is a science heavy podcast.

[David]

Very, very cool.

[Megan]

I like it.

[David]

Yeah. It's called identification of predictive Risk factors for the development of a Stress Fraction Fracture within six months in highly trained female long distance runners. A prospective cohort study, it took 21 elite female runners and then it studied them for six, six months, doing 118 total dexas overall.

[Megan]

And they found that nine out of 21 of these runners sustained stress fractures. And some of these were multiple stress fractures, as you can see by the numbers. So four of these stress fractures were in the sacrum, three in the tibia, three in the calcaneus, two in the pubic bone, two in the femoral neck, one in the rib.

[David]

Yeah.

[Megan]

One in the cuboid, and one in the metatarsal.

[David]

I feel like when you're seeing a rib stress fracture, you're seeing a high risk cohort heart too Yeah, I see.

[Megan]

That sometimes in rowers. I've actually almost never seen one in a runner in isolation. Yeah.

[David]

And there are, you know, injuries there that are. What was it called? Oh, trabecular bone.

[Megan]

Bone, and that's more hormone sensitive bone, which indicates like in the calcaneus or in the pubic area or in the sacrum, there's higher density of trabecular rich bone, which is more hormone sensitive. Which means that if you're sustaining a stress fracture there or bone stress injury there, it's more likely to be related to low energy availability.

[David]

So a super cool study. So DEXA scans looking at bone density we can see in advance. All right, well, would you doing DEXA scans in advance help you understand risk profiles? It would seem like it would. And sure enough, that's what the study found. DEXA results were significantly associated with stress fracture development. And most significantly, Lumber SP lumbar spine readings were the strongest predictor with going under 81.1% of the young adult mean being the level that showed highest risk.

[Megan]

And this is a little bit different than how we think about DEXA scans. In the US we often often use Z scores or sometimes T scores, depending upon the population. And this was actually done in Japan, which is why they're comparing it to the young adult mean. That's the convention that's not really used here. But those are low numbers. And whole body was also related to the whole body bone density, but the lumbar spine was the most relevant predictor.

[David]

So what's your conclusion for athletes that might be thinking about this in a general way? It's like, all right, a lot of our listeners, whether they have dexas or not, not understand that they have low bone density. Like, where do you go from there if you're seeing that? Okay, if you're below a certain point, like, bone density is not destiny, you know, and it's not just being a little bit below is a big deal, but if you're a lot below, how do you confront this in your running life?

[Megan]

Well, I think the first thing to think about is it's important to get adexa. I tell anyone that's had like irregular menstrual cycles, a history of disordered eating or eating disorders, get ADEXA now, because sometimes you can exists at in low bow density places for a long time without getting stress fractures or bone stress injuries. And then they seem to come on all at once and it's hard to get out of that cycle. And so it's like get that knowledge on board first.

[David]

Yeah, and it ends up being like validation of your approach to more carbs after a while. Is that that really plays a role. Vitamin D, calcium and generally giving your body the chance like yes, you're going to get these readings and yes, that might increase some of your fracture, your risk. But only in very rare circumstances does that mean you should not run. And I think that leads us to a question here from a listener. I was wondering if I might be able to ask you for some advice. I think I'm at the end of the road with running. I've been at it for four years and still haven't been able to string together a long period of injury free running. Despite very slow builds, strength training, working with a coach and health professionals, et cetera. I got a DEXA scan for the first time yesterday which revealed a negative 1.1.7 Z score on the lumber spine. As a young female, I don't wanna give any identifying information very young female. But a healthy hip on the deck set, um, and bone stress is, isn't even the problem. I've mostly had a crazy tendency to rack up tendon issues. I'm concerned that my body just didn't develop properly due to restrictive eating at younger ages. And so is my coach who told me today that realistically it might be better for me to stop trying to run and either stick to cycling, which is basically what I've been doing for the last year's anyway, or try to find another sport or hobby that my body can tolerate. To be completely honest, the idea of quitting running breaks my heart. It's my escape, my quiet space, and it makes me feel so alive while giving daily sport a purpose. But I think my coach might be right and it might be time to step away now. When a new injury comes up, it hurts me more and more because it becomes harder to continue feeling hopeful that I can one day leave the injury cloud. But my coach doesn't seem to understand why I'm so satisfied about it. He tells me sports shouldn't be my whole life and I'm feeling sad about leaving running. I need to work on my relationship with sport in going on. I was wondering if you have any advice for dealing with this situation. How am I meant to walk away from running and feel okay about it?

[Megan]

Well, the sister talks about heartbreak and my heart actually kind of breaks hearing this and hearing the coach's advice because I don't think this is a situation where you should walk away from running. In fact, I think there's very few situations in which you should walk away from running. And we certainly had those. Like, we've had athletes that have come to us with much worse DEXA scans and long histories of bone injuries. And it's like, okay, well, let's step away for a period of time. Yeah.

[David]

And we've done long resets where two.

[Megan]

Years, three years, but we're always getting them back.

[David]

Like, I mean, we've had athletes that they said negative one. Seven.

[Megan]

Oh, we've seen negative 3.8, negative four.

[David]

I think we've seen negative four plus negative 4.5.

[Megan]

Yeah, we athletes are coming back. We've seen some very bad DEXA scans. And, you know, this is in the category. It's also a young athlete, too. Like, this is the time in which you can build that bone density. And I think you can also do that. As long as you're feeling your body, as long as you're doing strength work and are carrying, committed to health and having a regular period, you can do that while running. And I think keep that hope alive. Because sometimes I think that hope, as long as it's done, as long as the hope is feeding a healthy context. Like, sometimes athletes need to step away to heal from disordered eating or eating disorders. And that's beautiful. But if it's being done in a healthy context, I don't think this is a situation where you have to step away.

[David]

Yeah. I mean, if we could look, if we had DEXA scans for every part of our physiology. Right, right. You would find things that seem like destiny throughout, that you would find things.

[Megan]

That already feel like fractures. Yeah.

[David]

Not. Not just in, obviously, your bone density, but if you were able to measure everything. We are all working with disadvantages in different ways. And, you know, for this person in particular, I imagine there's a tendency to really beat yourself up about what happened in your teen years and don't like, you are coming from a. There are so many athletes I've seen in this situation, and by so many, I mean thousands that have reached out to us, and every single one of them is able to work through it eventually. And that is the big message here is like, given a day, given a month. Yes, that much, much might not change. We've clearly said a lot of words here on this podcast today that are very complicated.

[Megan]

Are we getting to wizards fucking soon?

[David]

Coming ahead as soon as we end record, wizards be fucking boom. Wbs, thank you for breaking the tension for me a little bit. But with this listener, it's like if you zoom out a year or two years, the body is miraculous. It is so wild what you can see in ways that like, okay, I'm going through an injury right now and it does feel like I'm not going to be back for a while. And I feel that intellectually. But then I look at the athletes I have seen go through the worst and I'm like, they just kept showing up and eventually, eventually things reached a positive place as long as they kept giving that hope and giving their body the best chance. And so you're doing that stuff now. You're giving your body the best chance. We talked about this a lot before, but that means, you know, yes, tons of carbs. Passing the cheeseburger test. Like you maybe don't run until you can do things like eat cheeseburgers, even if it's not meat, like some stuff like that. You need to be healed from a fueling perspective. High dose vitamin D, if that's relevant to you, get your levels to tested. High dose calcium, you know, loading of the spine, doing your squats, your deadlifts, your military presses, things like that, getting strong. But if you can do that, the things that can happen when days add up into weeks, add up into years is just unfucking believable. And give yourself the chance to do it, even if like your current support system isn't the one to do it it with.

[Megan]

And I think give yourself grace too. Because bone density is complicated. It's multifactorial. Like a lot of this is genetic based, even up to Sometimes there's estimates 60, 65% of this could be genetic.

[David]

Based and they actually know the genetics that contribute. So it's not just decisions or anything like that.

[Megan]

So much more complicated, which is wild. I was actually part of a research paper that was looking at developing, you know, taking from 200,000 different places within the genome and using that to think about what is potential risk, risk for bone density or how does that predict bone density. And that to me is wild, is that like a lot of this is already set within your genetics. And give yourself grace for that. Or even things like taking medications like prednisone or prior history. And so this is complicated beyond just eating. And I think give yourself grace for that.

[David]

Yeah. And if we looked at everyone who's in their 20s that's listening to this podcast or even any age, but let's talk especially about the 20s, dude, we could just do a laundry list of things. Oh, so many things that are going to need to evolve, you know, the ones for you that are going to to need to evolve. Most of us didn't you go back to early 20s me? It's like, oh, my God, that guy has so much to learn. And that's why my breakthroughs happened at 36 years old and as an athlete. And it's like, well, if you told me at 22, it's like, keep grinding. It'll happen at 36, I'd have been happy about that. But I was like, well, why can't I just get better now? No, you just need to go through the path. Right? Like, it's like the. The journey is the destination, as my fortune cookie told me when we went to dinner.

[Megan]

And also, like, at the same time, biking can be great, too, and find context, like zwift and being outside on a gravel bike or whatever it is that you, like, enjoy about it too. And I think, yeah, make that journey as fun as possible.

[David]

Okay, final thing. Soft tissue injuries, like, tendon stuff up your protein for sure. Like, make sure you're getting plenty of protein. We're talking like, one gram per pound. Ish of body weight. You don't need to know your body weight, just, like, eyeball it. Generally, that will help you heal. Heal day over day and adapt in that sense, while you're also focusing on carbs. And then also, if you have tendon issues, maybe take collagen.

[Megan]

I was just about to say that mixed evidence collagen and vitamin C together can be super helpful. And might as well get some fly hair and nails while you're at it.

[David]

Dude, my. How my hair and nails look.

[Megan]

Actually, your hair looks great.

[David]

Okay, I have. I'm taking so much collagen right now. I did not take it until I got the MRI of my plantar tendon being so fucked. But, yeah, let's. Let's look. Nails.

[Megan]

Nails look good.

[David]

They've seen better days.

[Megan]

Do you even cut your nails or you just rip them?

[David]

I rip them.

[Megan]

Where do you put them?

[David]

I rip them while reading narrative reviews.

[Megan]

You just leave them on the ground?

[David]

It's just a little bit at a time. That's unfair.

[Megan]

That's unfair. You're like, I have my carb piles on the. On our pancake floor and my nail piles throughout the house.

[David]

No, I. I save them, and then I put them in the Whole Foods hot bar.

[Megan]

Collagen.

[David]

I'm just trying to give back.

[Megan]

That's organic matter.

[David]

There's actually probably some people in Boulder who wouldn't mind that.

[Megan]

No, it's true.

[David]

How's the hair looking?

[Megan]

Hair looks great.

[David]

Yeah.

[Megan]

You know, at baseline, it's. We've talked about this before. Your hair is little like pubes.

[David]

Yeah.

[Megan]

And it's like looking like some like big pubes. Yeah, yeah.

[David]

Big burly pubes.

[Megan]

WBF wizards are all about that.

[David]

I was gonna say BP for pearly pubes, but I think that might be a copyright infringement on British Petroleum or.

[Megan]

Whatever for blood pressure.

[David]

True. Okay, I think we probably shouldn't do any questions.

[Megan]

That was. That was a spicy one.

[David]

Yeah, we'll see.

[Megan]

We'll see, we'll see. What do you mean?

[David]

Oh, yeah. Well, I mean there's a lot in that episode because what we're about to record actually is the intro to the episode which going to be a vibe shift too. So. Yeah. Thank you all for being here with us in this journey.

[Megan]

It means a ton. Yeah.

[David]

We're experimenting with things as we go with the podcast. We just want to bring you joy and education and contribute to health and things and get you real fast. But man, sometimes it's hard.

[Megan]

Sometimes it's hard. Are we gonna be awake tonight at 2am with anxiety?

[David]

Nah. No, we're not gonna be awake at 2am, are we?

[Megan]

Well, last night Leo woke us up and he's like, where's my paw Patrol Band aid?

[David]

He has anxiety. He's not worried about narrative reviews. It's just human nature. Yeah. Okay, let's go on to the Janji ad. How about that?

[Megan]

Yeah, Janji. We love Janji. You know, that's a feel good way to end this episode. I'm like, what holes did we dig for our. But you know what? John G just has pockets.

[David]

Oh, amazing.

[Megan]

They're solving it all for us. They make us feel good.

[David]

So go to john g.com j a n j I dot com. You can get 15% off everything by joining the John G Collective. That's great. What do you want to promote today?

[Megan]

A lot of sales going on right now. The women's trail tight is on sale. I'm wearing it right now. Look at all these pockets.

[David]

Oh yeah.

[Megan]

I can fit a whole baby bottle in that.

[David]

This is really. I also like how the pockets are sheer so you can see what's in them.

[Megan]

I think it's cool. Actually in the photo from us from Leadville, you can see like my gels in there and it looks pretty authentic. Yeah. Also some Tylenol hanging on there too. Also, I love the multi short is great. And I'm just really vibing with a rain jacket too. I wear it on a lot of runs where it's not raining.

[David]

Yeah, the thermal runner is amazing. I've been using that for my heat suit and the men's Atlas pant. That's the one like, I recommend fully right off the bat.

[Megan]

You basically only wear wear that ever, ever. It's like running date night bed.

[David]

I order like one size up so it's really comfortable at all times. It just fits so good. And you can fit things in the waist belt. John's the best. Let's go on the listener corner. This is an uplifting one. I wanted to write a quick reply to this old thread. I think it was an ancient email because I finally became a Patreon subscriber. As I mentioned 1.5 years ago in this thread, I have been a very longtime listener to the pod. And when you moved to Patreon, I told myself that I would get it as soon as a gift for myself after finishing my PhD. Well, last Friday, I officially passed my defense.

[Megan]

Oh, hell yeah.

[David]

Gave a PhD in a scientific field. And more importantly, by 8:00pm that evening, I became a Patreon subscriber.

[Megan]

I'm so honored.

[David]

I'm super stoked to listen to all the bonus episodes and use your training plans. Thanks for bringing so much positivity through my Life. Through the PhD, I have listened to the pod while walking to work in the cold winters, while working in the hot room. Uh, during time course experiments. There's really cool details I am leaving out here because I think it might be identifying.

[Megan]

This is great science.

[David]

Yeah, there's a lot going on. Um, and of course, throughout the many runs that have also carried me through grad school. Thank you. And to Zah.

[Megan]

That means so much, but also hazard to a PhD. It's a big deal. Those are long, long journeys.

[David]

They also said, feel free to use this as listener corner so I can mention chemical biology PhD. There was radioactivity going on. And, you know, just a wild reflection on what happens when you keep struggling showing up, you know, like, it's so cool. And hey, if you're out there and you can't afford it, what this person should have done, just message us and you'll get it for free.

[Megan]

I know. I was like, can we comp them for their PhD defense? That's a big deal. Here is our gift to you.

[David]

Maybe that's what I'm gonna go.

[Megan]

We should go back and comp them.

[David]

I'm gonna go refund their purchase for life. For life.

[Megan]

Yeah. As long as they do good work in the field of science.

[David]

They don't let me do chemical biology. Patreon. That's just giving me Responsibilities. Responsibilities sound horrible right now. So instead of. Of that, if this listener just messages.

[Megan]

Me every year, every year, you will get a refund. 45 years for life.

[David]

So, hell, yeah. This is just the best news. And to everybody out there, we love you so much. The world is complicated. Life is complicated. Science is complicated. Podcasting apparently is complicated.

[Megan]

We got to the end of this, and I was like. That was. We were like, contrarians. We are not contrarians.

[David]

Can we do simple episodes next week?

[Megan]

I know was like, I was excited for this one, and we got three quarters of the way through, and I was just like, haven't. I'm like, Kevin on Home Alone, holding my face like, what did we do?

[David]

There's a moment in the science discussion of the carb where you're just like, we had been so contrarian for so long of. Of. Of the researchers. David, what the did you do to me?

[Megan]

Why do we have to do this? I feel like it's like we're, like, in Home Alone, and we're, like, coming at them with, like, all the defenses. We're like, we see this and this and this, and then it just doesn't stop.

[David]

But, yeah, we love you. Thanks for being here. If you want a simple episode, talk about Patreon. That is a place where last week we had this goofiest episode of all time.

[Megan]

I loved that episode. We just watched the Burrito League live camera. It was great.

[David]

And just did, like, a live announcing of it. They should hire us. So that's a slightly different vibe. And, man, I'm so proud of you, Megan. Actually, me, my very serious reflection is I was listening to the Beth MacKenzie discussion about. Of you, and it's one of the first times I've ever heard someone articulate what it is about you that is so special so directly. And the reason I cried was, you know, Beth said it beautifully. But also, knowing other people see you in the world the way that you are is just the most magical thing. And so I love Beth for doing that, because it's something like, when I am 90 years old, I want to come back to that and be like, what a life you. You lived. To take everything you've done, like the MD, the PhD, all of that, and channel it in this way that when someone reaches out to you and they're uncertain, and you're just like, fuck, yes, I've got your back. And that, to me, is everything.

[Megan]

Oh, that means so much. Why listen to it on the treadmill? And you know what? Honestly, I shat my pants just a Little bit. Just a very little bit.

[David]

Because of a bet suck.

[Megan]

No, no, no. I mean, it was a hard workout. We had Nepalese food that was amazing the night before. But you know what? It was not great on the treadmill. And me and my stubborn little self. The bathroom was right there. And I was like, I don't want to ruin my beautiful heart rate chart, so I'm going to stay on here.

[David]

Nope.

[Megan]

I needed it in that moment. I really needed it in that moment. So thank you. Like, it meant a lot. And, yeah, it was counteracting some literal shit. Sometimes that happens. We don't talk about that enough. Actually, it doesn't happen to me all that much.

[David]

No. No, not very often.

[Megan]

One circumstance that I was just like.

[David]

Man, that's a David thing. I came into the room. Yes. There were some tears still flowing down your face. And you didn't look at me and say anything about the Beth episode at first. All you did is look at me and just made a little, like your fingers doing a little bit. You're like, I pooped myself a little bit.

[Megan]

Just a little bit. A little bit.

[David]

I'm like, did you get off? You're like, nope, nope. And I'm like, okay. And then you got off a few minutes later and did the. I'm gonna say something I probably shouldn't say to end the episode.

[Megan]

Oh, you should just do it.

[David]

The bathroom equivalent of that narrative review. Sorry.

[Megan]

Bye.