Loading summary
Transcript1 lines
- [00:00]
A
Only about 5 to 6% of American adults meet the adequate fiber intake. That means roughly 94% of this country is falling short. There was a recent 2025 case of a 45 year old woman eating an enormous amount of pears and developing a complete small bowel obstruction requiring a surgical removal. She had no risk factors other than the sheer volume of fiber and pairs the G8. Nearly half of patients discontinue GLP1 therapy within one year, with GI side effects hitting the primary driver. And when you use a medication that delays gastric emptying, on top of that, your stomach is essentially like a big traffic jam. Food sits there longer, gas accumulates, bloating intensifies and nausea worsens. So this is the same pathophysiology we see in something called gastroparesis or stomach paralysis. But the reality is GLP1 receptor agonists and dietary fiber are not opponents, they're partners. But these partners need to learn how to dance better. With all this talk about fiber, this brings us to what I think is the most underappreciated consequence of the GLP1 revolution. Do I think we should fiber max or fiber men? I think we. Our prediction is fiber will be the protein of 2027. I remember when Metamucil was the only talked about fiber supplement. And now the Arnold Schwarzenegger pump club also includes, you guessed it, fiber. There's a trend online right now called fiber maxing, and it's exactly what it sounds like. Creators pushing 40, 60, sometimes 80, even more grams of fiber a day to control appetite, support gut health and drive weight loss. You've probably seen the version of this where someone masses out on a large daily dose of psyllium husk for a month and then reports dramatic weight loss. There was a recent 2025 case of a 45 year old woman eating an enormous amount of pears and developing a complete small bowel obstruction, which means, number one, this is a medical emergency. Bowel obstruction means they cannot pass gas and they cannot go to the bathroom. All of this from a per bezoar, which is a kind of like a large ball of fiber. And persimmons are the most usually implicated source of this phytobezor. Think of like a cat hairball. And it's due to their high tannin content, which is a compound that somehow creates this ball. 23% of these bezoars are dissolved with Coca Cola. So there are pros and cons to fiber and a diversity of fibers, which is what you want in the diet, but before we get into the numbers, is this fiber trend even directionally? Right. And mechanistically sloppy? Well, your microbiome. Does it even matter? And most Americans genuinely are undereating fiber. Turning a nuanced nutrient into a single number. It's kind of like protein. To maximize it is the same mistake that we did with protein. Just to sum this up, should we be fiber maxing or should we not? Well, I'm going to let you decide, but I'm going to show you both sides. The FDA daily value for fibers, 28 grams a day. And this is based on a 2,000 calorie diet. I don't know the last time it changed. And this is what appears on the back of a food label. Only about 5 to 6% of American adults meet the adequate fiber intake. That means roughly 94% or 95% of this country is falling short. And this is not a new problem. A 2024 New England Journal Medicine review of the NHANES data, which is the data set that is typically quoted, found that 94% of Americans age 1 and older, basically everybody, missed the adequate intake for their life stage, with adults 20 and older averaging just 17 grams a day. And roughly that's half of what is recommended. So the Academy of Nutrition and Dietetics found the same pattern with only about 5% of the population hitting the target of 14 grams per 1000 calories. So this is a ton of words to just simply say we are under eating fiber. Two decades of nationally representative data and the needle has barely moved. So no, fiber is not a solved problem. But here is the reason I chose fiber maxing for this episode. The GLP1 fiber paradox. Why the drug that needs fiber makes fiber hard to eat. And again, this is a class of drugs. The GLP1 receptor agonist we've all heard about. Semaglutide, tirzepatide, Ozempic, Wegovy, mounjiorno, zepbound. The list goes on. There are new emerging ones. All of these may need to start out with a fiber mining diet. Yeah, first time you're hearing it. Fiber mening. And here's the paradox. These drugs desperately need dietary fiber to work optimally. But they also make fiber incredibly hard to tolerate. The GI side effects that make fiber hard to tolerate, and they're not rare. 40 to 70% of patients on a GLP1 receptor agonist experience GI adverse effects. Most common, nausea, bloating, constipation, vomiting and diarrhea. And in the major weight loss trials, GI disorders were reported in 74 to 84% of participants on one particular medication, nearly half of patients discontinued GLP1 therapy within one year with GI side effects, you guessed it, being the primary driver. So if we layer on GLP1 use, these drugs, reduce appetite, they increase early satiety, they decrease overall food intake, and that's how they're supposed to work. But of course, when total food volume drops, fiber intake drops with it. And a secondary analysis of L glutide randomized control trial found that patients on GLP1 therapy under consumed multiple key nutrients relative to the recommendations. Now, they weren't just eating less, they were eating less of the things that they need the most. So we have a population that's already fiber deficient, we put them on a medication that further reduces their food intake and causes GI symptoms that make fiber even harder to eat. And then frankly, we wonder why they're constipated, bloated, losing muscle mass, also losing fat. To understand this paradox, let's just briefly touch on the GLP1 receptor agonist and how it works. It works in part. You take these medications and they slow gastric emptying, meaning the food stays in your system longer and it also slows motility, meaning the movement of the gut. This is not a side effect. I just want to be very clear, this is a mechanism of action as to how these medications work. They reduce glucose absorption, they increase satiety, meaning you're not hungry, and promote weight loss. The same mechanism is exactly why fiber becomes a problem. High fiber foods, they're already slow to digest, which is why they say eat fibroid will affect your appetite. They're bulky, they require gastric processing time. And when you use a medication that delays gastric emptying, on top of that, your stomach is essentially like a big traffic jam. Food sits there longer, gas accumulates, bloating intensifies and nausea worsens. So this is the same pathophysiology we see in something called gastroparesis or stomach paralysis. This is a chronic disorder where the stomach takes too long to empty it. It, you know, it's, we see it a lot in diabetes because of the nerves where the stomach just has food in it, the intestines just have food in it. And GLP1 receptor agonist can cause frank gastroparesis. So a sudden stopping or slowing. And many of the advisory boards specifically warn that high fiber foods, AKA fiber maxing, should be avoided during the first few days of treatment because they can compound the delayed gastric emptying. So I hope all of this is clear when the question comes, should we be fiber maxing or should we be fiber mining? It depends. And man, I remember when I was in my residency I had to go and disimpact patients with the glove, the whole thing. I am telling you, I don't know what it's like for the residents now, but it's exactly what it sounds like. It. It's not just whole fiber foods, so we're talking about fiber supplements as well. Psyllium, guar gum, they have all been reported to cause these pharmacobezoars, that big hairball which is AKA fiber or AKA some kind of ball. But just imagine the cat hairball in patients with older GI motility. So many individuals. Or there have been many cases where people develop bezoars. Again, I'd mentioned there was that case of the 45 year old woman. She had no prior GI history. She ate a ton of pears and developed a phyto bezoar that completely obstructed her requiring a surgical removal. She had no risk factors other than the sheer volume of fiber and pears that she ate. Okay, so there's been a series of. Most recently I was looking at the data. 87 intestinal bezoar cases due to vegetable fiber. And of course many of them did not have a predisposing factor, meaning they didn't have an illness that goes with it. So imagine that same scenario in a patient whose gastric emptying is already slow because they're on medications. So the risk calculus changes. Okay, so what about fiber maxing? This of course goes back to fiber supplementation during GLP1 therapy. Well, this may actually help manage the GI side effects, but it makes fiber hard to tolerate in a 2026 perspective. In the Journal of Nutrition, there was analysis that showed that fiber supplementation of course improves bowel function and stool consistency. And directly addressing the constipation and diarrhea that are among the most common side effects with GLP1. Use gradual increases in both soluble and insoluble fiber for constipation management. Things like prunes and dried fruit and fiber capsules or powders for diarrhea to provide stool bulk. The same substance that can worsen nausea and bloating during dose escalation can also relieve constipation and normalize bowel function. With all this talk about fiber, this brings us to what I think is the most underappreciated consequence of the GLP1 revolution. Do I think we should fiber max or fiber men? I think we. Well, it depends but sarcopenia is a major problem and that's a decreased muscle mass and function. And GLP1 agonists cause weight loss. That's totally the point. But not all weight loss is equal. And in the major trials, approximately 25 to 40% of weight loss on GLP1 therapy is lean mass. So for a 70 year old who is already constipated, that's not just a number on a DEXA scan, that's functional independence. That's a ball risk. That's the difference between living at home and living in one of the facilities that I used to round on. And the JAMA International Medicine, the joint advisory, they recommend the need for protein at 1.2 to 1.5 grams per kilogram. So if someone is on GLP therapy, in order to preserve muscle mass, people need to train. And despite the decreasing appetite, they need to make sure they're getting adequate protein, which is already a challenge. And getting adequate fiber on top of that might feel impossible. Okay, so what is your takeaway? GLP1 receptor agonist and dietary fiber are not opponents, they're partners. But these partners need to learn how to dance better. And the drugs that slow the gut fiber feeds the gut and the microbiome kind of sits in the middle, translating fiber into these very important metabolites that support the drug's efficiencies. So we have short chain fatty acids, endogenous GLP1 production, which means your body makes GLP1 and then essential amino acids. So if we get the balance right, you have a synergistic system. Pharmacology and physiology work together through the gut microbiome. If you get it wrong and you fiber max too much, too fast or fiber men don't get enough fiber at all, you get side effects, non adherence, muscle loss, and a gut microbiome that's kind of a mess with side effects like bloating, constipation and nausea. So again, this prescription pad of the medication, that's only one half the other half of the plate, is designing a whole foods diet with both protein, fiber, carbohydrates and fats. Till next time, thanks for listening. And friends, eat your fiber slowly. Stay forever strong.