Weight Loss: Why Won't It Stick?

Summary

Podcast Summary: Science Vs – "Weight Loss: Why Won't It Stick?"

Date: August 6, 2026
Host: Wendy Zuckerman, Science Vs Team
Guests/Experts: Rose Rimler (Senior Producer), John Rossi (Musician and Drummer), Alyssa Hasty (UT Southwestern Medical Center), Faith from University of Copenhagen, Jamie Hartmann-Boyce (UMass Amherst), and various listeners.

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Overview

This episode tackles the persistent and demoralizing struggle many face: why is it so hard to lose weight and, more importantly, keep it off? The Science Vs team explores whether “yo-yo dieting” or “weight cycling” damages metabolism, health, and body composition, or if internet and influencer warnings are exaggerated. The show features personal stories, leading experts, and critically examines the scientific literature to separate myth from fact.

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Key Discussion Points & Insights

1. What is Weight Cycling? (00:03–04:29)

• Definition: Weight cycling (a.k.a. yo-yo dieting) means losing and regaining weight repeatedly.
• Prevalence: Up to half of U.S. adults have experienced weight cycling, many repeatedly.
• Personal Impact: John Rossi, a drummer, shares:

  “I have been weight cycling most of my adult life and it’s not fun.” (01:12)

• Emotional Toll: Listeners describe frustration, sadness, and self-blame after relapses.

Memorable Quotes

• John Rossi: “I would take every other challenge in my life and double them if I could get rid of this one.” (04:12)

---

2. Internet Claims About Weight Cycling (05:33–06:27)

• Common Claims: Online sources suggest yo-yo dieting "wrecks metabolism," increases body fat percentage, ruins health, and is worse than never dieting.
• John Rossi’s Desire for Science:

  “I just want to hear from people that I trust, like a true scientific look at all of this, because I can’t. I can’t.” (06:27)

---

3. Is Long-Term Weight Loss Possible? (09:29–11:44)

• Rarity of Success: The National Weight Control Registry was created to study those rare individuals who lose significant weight and keep it off. Most people can't.
• Common Traits among ‘Success Stories’:
  • Regular breakfast eating
  • High levels of exercise (avg. 1 hour/day)
  • High dietary restraint
• Rose Rimler: “It has to become very important.” (11:44)

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4. Why Is It So Hard to Keep Weight Off? (11:53–14:59)

• Biological Adaptations:
  • Weight loss changes hormones that increase hunger and decrease fullness.
  • The body unconsciously nudges individuals to eat more after weight loss.
• Hunger Hormone Study:
  • People unknowingly excreting more calories began eating more automatically (12:35–13:45).
• Metabolism Slows Down:
  • Losing weight makes the body require fewer calories since it’s "running a smaller machine.” (15:15–15:58)

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5. Does Weight Cycling “Break” Your Metabolism? (15:59–20:24)

• The Biggest Loser Study:
  • After losing and regaining weight, former contestants’ metabolism was suppressed by ~500 calories/day, even after regaining weight (17:45–18:51).
  • Faith: “So the resting metabolic rate was lower than predicted by about 500 calories per day.” (18:38)
• But!
  • This was a small, extreme sample—findings are not generalizable.
  • Broader, less extreme studies and meta-analyses find only minor, if any, lasting effects; differences may fall within margins of error (19:39–20:20).
• John Rossi:

  “That’s really encouraging. I’ve been told by so many people... that I am hurting myself.” (20:34)

Takeaway

Most scientific evidence suggests typical weight cycling does NOT permanently or seriously "wreck" metabolism for most people.

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6. Impact on Muscle vs. Fat (21:12–24:21)

• Body Composition Fears:
  • Concern: Each cycle means you lose more muscle, regain more fat.
  • Study 1 (Older Adults, NC): After cycling, more weight was regained as fat (88%) than as muscle (only 12%). (22:08)
  • Study 2 (Younger Adults, Germany): Regain was proportionate—lost and regained similar ratios of muscle and fat. (22:55)
• Age as a Factor: Older adults tend to regain more fat than muscle; younger adults don’t see the same problem.
• Evidence for Compounding Issues: Lacking—few long-term studies across multiple cycles.

---

7. Does Weight Cycling Make You Sicker? (28:02–37:40)

Inflammation and Immune Function (28:34–33:15)

• Fat as Active Tissue: Visceral fat stores immune cells, which can cause chronic inflammation if overstressed.
• Mouse Study: Mice who weight cycled had higher immune cell (T cell) activity/inflammation than controls, even at the same body size.
  • Alyssa Hasty: “The body remembers, the immune system remembers our body weight and gains and losses in that.” (32:17)
• Uncertainty in Translation: Mechanism in humans is unclear.

Human Studies: Health Outcomes (33:18–37:40)

• Observational Studies:
  • Weight cyclers had higher risk of heart failure and death compared to stable-weight individuals, but these were not randomized; causality uncertain.
• Randomized Controlled Trials (RCTs):
  • Jamie Hartmann-Boyce: People who lost weight in ‘healthy’ ways (diet & exercise), even if they regained it, were STILL less likely to get type 2 diabetes, had lower cholesterol and blood pressure than those who never lost weight. (35:10–35:31)
  • Healthiest behaviors (exercise, more fruit/veg, less smoking/drinking) were more strongly linked to lower death risk than weight itself.

Memorable Quotes

• Jamie Hartmann-Boyce:

  “Even if you started a certain weight, did your diet and exercise program, you stopped it, you went back to your starting weight, compared to someone who had stayed at a stable weight the whole time... you were still less likely to get type 2 diabetes.” (35:10)

• Rose Rimler:

  “The thing that mattered the most for, you know, death was not your weight, but the healthy habits that you did.” (36:52)

---

8. Key Takeaways and Closing Thoughts (37:40–40:13)

• Do healthy things:

  • The science suggests healthy habits (regardless of weight loss success or cycling) are what matter most for long-term health.

• John Rossi:

  “People don’t know what they’re talking about with this stuff all the time... I should worry more about... what the science says than what people tell you.” (38:32)

• On self-esteem and identity:

  • John reflects on clothes, confidence, and not letting social pressure (or science myths) dictate self-worth.

---

Notable Quotes & Moments (with Timestamps)

• On Emotional Cost:

  “It is. I would take every other challenge in my life and double them if I could get rid of this one.”
  John Rossi [04:16]

• On Traits of Weight Loss Maintainers:

  “They exercise a lot. On average. An hour a day, these folks.”
  Rose Rimler [11:19]

• On Biological Set-Points:

  “Keeping off weight is like holding a rubber band really tight...”
  Rose Rimler [14:11]

• On Metabolic Slowdown:

  “So the resting metabolic rate was lower than predicted by about 500 calories per day.”
  Faith [18:38]

• On Research Limitations:

  “This is a tough one because... some researchers are genuinely worried about this, but... I didn’t see any evidence that’s the case [that you ruin your body composition].”
  Rose Rimler [23:54]

• On Inflammation – Mouse Study:

  “The T cells were elevated even further in the weight cycle compared to the obese, only group.”
  Alyssa Hasty [31:33]

• On Healthy Habits vs. Weight:

  “The thing that mattered the most for, you know, death was not your weight, but the healthy habits that you did.”
  Rose Rimler [36:52]

• Final Message:

  “I should worry more about... what the science says than what people tell you.”
  John Rossi [38:32]

---

Important Segment Timestamps

• 00:03 – What is weight cycling?
• 04:29 – Listener and guest stories
• 09:29 – Is long-term weight loss possible? Traits of "maintainers"
• 11:53 – Why is it so hard to keep it off?
• 14:59 – Does weight cycling “break” your metabolism?
• 17:45 – The Biggest Loser study
• 21:12 – Impact on fat vs. muscle over cycles
• 28:02 – Inflammation, chronic disease, weight cycling
• 33:18 – Human studies: disease risk
• 37:40 – Takeaways on behaviors, not weight
• 39:07 – John Rossi’s final thoughts about self-esteem

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Conclusion

Science Vs finds that while weight cycling is emotionally taxing and seemingly “bad,” the purported dangers are often exaggerated. Biological and societal forces make weight loss hard to sustain. The bulk of scientific research suggests that, for most people, weight cycling does NOT irreparably destroy metabolism or muscle. Health outcomes are more strongly linked to maintaining healthy lifestyle habits—more exercise, fruits and vegetables, less smoking and drinking—than to one’s BMI or weight history. This reframing can help individuals focus on meaningful health changes instead of succumbing to shame or myths around dieting.

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Bottom Line:
Weight cycling is common, emotionally hard, and frustrating, but the best available science does not show it destroys your metabolism or health. Focus on positive behaviors—not the number on the scale—for long-term well-being.

Transcript

[Wendy Zuckerman]

Wow, wow, wow.

[Sponsor/Ad Voice]

So it's real.

[Rose Rimler]

It is true.

[Wendy Zuckerman]

It is true that weight cycling can mess up your metabolism.

[Rose Rimler]

Not so fast.

[Wendy Zuckerman]

Hi, I'm Wendy Zuckerman and this is Science versus. Today on the show. Why is it so hard to lose weight and keep it off? Plus, what happens to your body when you lose a bunch of weight and put it back on? And lose a bunch of weight and put it back on? Because the Internet is saying that this cycle, which is very common, is actually really, really bad for your health. But is it true? And just quickly, before we get started, I do want to say that if this is a sensitive topic for you, please take care while you're listening to the show and we're going to put some resources in our show notes.

[Sponsor/Ad Voice]

Okay?

[Wendy Zuckerman]

To get into the science, here we have senior producer Rose Rimler. Hello, Rose.

[Rose Rimler]

Hi, Wendy.

[Wendy Zuckerman]

Where do we begin?

[Rose Rimler]

The first thing I want to do is I want to introduce you to someone I recently talked about this quite, quite a bit with. His name is John Rossi. He's a musician. He's actually a drummer. I called him up because he is someone who has struggled a lot with his weight.

[John Rossi]

I have been weight cycling most of my adult life and it's not fun.

[Wendy Zuckerman]

Weight cycling. So this is the term for when folks lose a bunch of weight, Put it back on. Lose a bunch of weight, put it back on. Right. Is this. This is the new Internet term that I guess in the 90s we were calling yo yo dieting?

[Rose Rimler]

Yeah, I think so. I think beat cycling is like a little bit more. Sounds a little more scientific or something. And so John's story is that he initially lost a lot of weight in his 20s. That was like the first time he ever lost weight. He lost quite a bit of weight and his appearance really changed. People, he said, were complimenting him a lot. He was getting a lot of positive attention and it changed a lot of things for him. He said it changed the way that he dressed. So he said that before this happened, he was wearing like dark T shirts and baggy jeans.

[John Rossi]

And now I was wearing the most, like funky pink cool stuff and skinny jeans. And I was in it to win it.

[Rose Rimler]

What was your wackiest outfit from that time?

[John Rossi]

I had. So I had a pink T shirt that I like to wear with a pink, like flannel overshirt, like a button down over it, unbuttoned with matching pink sunglasses.

[Rose Rimler]

That sound pretty rad.

[John Rossi]

It was so bright and it was so good and I miss it.

[Rose Rimler]

He eventually gained back a lot of the weight that he had lost. And so he put his pink outfit in the basement. So that was the first time. But he's since then gone through a bunch of these cycles. Losing weight, gaining back weight, losing weight, gaining back weight. And he's not alone. Studies find that up to half of adults in the US have gone through at least one weight cycle.

[Wendy Zuckerman]

Half of, of all adults in the US have experienced this.

[Rose Rimler]

Yeah, it's very common and it's also very common for it to happen repeatedly. So another survey found that of people who do weight cycle, they go through on average eight cycles by the time they're middle aged. And, and you know, he's right on track for that average.

[John Rossi]

I am currently on my ninth time trying to lose weight.

[Wendy Zuckerman]

Wow.

[John Rossi]

And how much, counting that first one,

[Rose Rimler]

how many pounds do you think that is over the course of your life?

[John Rossi]

I mean, if I had lost all of this together, I, I, I'd be in the negatives.

[Expert/Researcher]

Yeah.

[Rose Rimler]

You've like lost your entire self.

[John Rossi]

Yeah, yeah, yeah. Like I have lost multiple people, you know, over this, this time period.

[Rose Rimler]

In fact, he says he's lost and put on hundreds of pounds over the last couple of decades.

[Alyssa Hasty]

Yeah.

[Rose Rimler]

You know, John has worked so hard so many times that when this happens, it just feels awful for him.

[John Rossi]

Terrible. Like, truly like I was failing myself and I was, I was, you know, I had succeeded at something and then failed at it, which I think is probably worse than just never succeeding at something. And it's really hard. It is. I would take every other challenge in my life and double them if I could get rid of this one.

[Expert/Researcher]

Yeah.

[Rose Rimler]

And I heard similar things from other people who I spoke to for this episode. Listeners called in and just seemed like there was a really common theme of frustration, sadness, and then also a lot of self blame.

[Expert/Researcher]

Ugh.

[Elena]

You know, I've done it again. I just couldn't help myself, or I wasn't paying attention or I wasn't doing what I was supposed to be doing.

[Wendy Zuckerman]

I don't know how to get out of this cycle.

[Caller/Listener]

When I was with a bunch of friends and had to climb on a scale in front of a bunch of people to be weighed to see if I could ride a ride at a carnival. And my weight was right back up to where it had been out over where it had been before. I started Weight Watchers three years before. I was devastated and went into a depression spiral that lasted for years.

[Expert/Researcher]

Oh.

[Rose Rimler]

So people really want to know more about why this happens to them. And in this episode we are going to get into that yeah, but we're going to get into more because beyond sucking, which it clearly does now, there's a lot of Internet claims that say that this is actually bad for your health.

[Wendy Zuckerman]

Cue the influences, Rose.

[Rose Rimler]

Yo yo dieting is so bad for us. Not enough people are talking about how damaging repeated weight loss and regain can be.

[Wendy Zuckerman]

It wreaks havoc on our body's internal processes and the infrastructure that keeps us alive. Yo yo dieting is killing you.

[Rose Rimler]

And specifically what people talk about is that you're like ruining your metabolism, that you're going to end up with higher body fat percentage and less muscle than you would have otherwise, and that you're just, you're going to be sick, you're going to get diseases like type 2 diabetes, heart disease, that kind of thing.

[Wendy Zuckerman]

And you would have been better off if you just never, never tried at all. Kind of is the implication.

[Rose Rimler]

Some people say that. So we're going to get into all of that. We're going to do that for John, too. John is a very sciency person, but he says this one, this is kind of hard for him to dig into.

[John Rossi]

This one's too close to home. I've read so many things, I've heard so many things. I just want to hear from people that I trust, like a true scientific look at all of this, because I can't. I can't.

[Wendy Zuckerman]

At this point, I really felt like, do, do, do, do, do, do.

[Rose Rimler]

Rose, you got your cape, your invoice. We trust. Oh, I have my cape. It's my cape, actually.

[Wendy Zuckerman]

Yeah, yeah, yeah. I'm just in costume.

[Sponsor/Ad Voice]

I'll be the voice.

[Wendy Zuckerman]

Yes, the science on weight cycling. And is it really killing you? Coming up after the break,

[Sponsor/Ad Voice]

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[Expert/Researcher]

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[Wendy Zuckerman]

Welcome back. Let's find out why it's so hard to lose weight and then keep it off. Because it's because everything's political these days. It actually almost feels like the woke thing to say is it's so hard to lose weight and keep it off. And the people who say it like it is, they'll tell you if you diet and keep that diet, you can lose weight. You know. So is this just wokeness and unwokeness, gone mad or give me some actual data here.

[Rose Rimler]

I mean, if it were that easy, we wouldn't have things like the National Weight Control Registry, which is set up to specifically find people who can lose a lot of weight and keep it off and track them and study them. That's how rare it is to lose a significant amount of weight and keep it off for longer than like a year.

[Wendy Zuckerman]

Right.

[Rose Rimler]

And one person I spoke with, Elena, she's an actor from New York, she had heard about this registry that was

[Elena]

like my goal was like, I want to be in the registry. So I guess like, you know, if people do lose a bunch of weight and keep it off long term, is there anything.

[Rose Rimler]

What's special about them?

[Elena]

What special about them? Are they addicted to exercise and psychotic about what they eat and that's the only way you can do it?

[Wendy Zuckerman]

Great question, Elena. What's happening is, is that, is that what's special about them?

[Rose Rimler]

Well, the scientists behind the registry have Shared some things that these people seem to have in common. Some of them are kind of random. Like, they tend to eat breakfast.

[John Rossi]

Oh.

[Rose Rimler]

So take with that what you want.

[Sponsor/Ad Voice]

Okay.

[Rose Rimler]

They also exercise a lot. On average. An hour a day, these folks.

[Wendy Zuckerman]

An hour a day. Yeah. That's committed.

[Sponsor/Ad Voice]

Yeah.

[Expert/Researcher]

And.

[Rose Rimler]

And to Elena's point, like, are they, I think she said, psychotic about what they eat? I don't know if they're psychotic about it, but they're very careful. The researchers said that they exhibit, quote, a high level of dietary restraint.

[Caller/Listener]

Mm.

[Wendy Zuckerman]

So it really becomes their whole life.

[Rose Rimler]

It has to become very important. Yeah.

[Wendy Zuckerman]

Okay, so then why is it.

[Rose Rimler]

Why does it take so much?

[Wendy Zuckerman]

Why does it take so much? That's right.

[Rose Rimler]

Yeah. So there's a few reasons. One is that when you lose weight, your hormones change, your hunger hormones increase and your fullness hormones decrease.

[Wendy Zuckerman]

So if you. To this point of. If you just stayed eating a certain number of calories that allowed you to lose weight in the first place, if you just stayed on that diet forever, you could keep this weight down. Actually, staying on that diet forever becomes harder and harder.

[Rose Rimler]

Yes, it becomes harder and harder because your body is nudging you towards eating more to counteract that weight loss. And there's a really cool study I want to tell you about that shows this and shows just how, like, below conscious awareness this is happening.

[Wendy Zuckerman]

Yeah.

[Rose Rimler]

So in this study, researchers gave people a drug that pulls sugar out of your body and into your urine, so you end up peeing out a lot of sugar. This is in the diabetes world, this drug.

[Wendy Zuckerman]

Okay.

[Rose Rimler]

Because you're peeing out a lot of sugar, you lose weight, you're, like, excreting calories. So people on this drug tend to lose weight.

[Wendy Zuckerman]

If you tasted your urine, it would be sweet.

[Rose Rimler]

Yes.

[Elena]

Okay.

[Rose Rimler]

You know, if you run out of honey, you know, it's good to have a little backup. This was a controlled study. They also had people take a placebo pill. They had another group on a placebo pill. So if you were in the study, you didn't know if you were given a pill that was causing you to excrete more calories or not.

[Wendy Zuckerman]

Okay. Huh.

[Rose Rimler]

Then they followed people to see kind of like, how they ate after that. And they found that the people on the drug, without knowing that they were losing weight, started to eat more. The people on the placebo drug note, there wasn't that kind of change.

[Sponsor/Ad Voice]

Right.

[Wendy Zuckerman]

So just like those hunger hormones kicking in, they were just a little bit more hungry.

[Rose Rimler]

Just a little bit.

[Expert/Researcher]

Yeah.

[Rose Rimler]

But it adds up.

[Wendy Zuckerman]

So this is one reason why it's so hard. Your body wants to conserve calories, which for most of human history we were hunting for food. Food was hard to get and that's how humans evolved. And now it's very different. So it makes, it does make perfect sense that there are these things beyond our control in our body that are pushing us towards weight gain rather than weight loss.

[Rose Rimler]

And I think this is why it's so confusing and frustrating for people because they're still eating below what they want to eat. They're still like restricting their, their dietary intake. I heard someone give a talk where they said keeping off weight is like holding a rubber band really tight. So you have to keep holding it and it's very hard to do that. Eventually you relax a little bit. And another thing that people bring up is about metabolism, this idea that your metabolism changes from weight loss. And that's another factor.

[Wendy Zuckerman]

That's right, because people, the people who say that weight cycling is dangerous, wasn't one of their arguments was that it actually breaks your metabolism in the end. Right, right. Therefore making it even more difficult to lose weight.

[Rose Rimler]

Yeah. So let's, so let's dive into metabolism.

[Wendy Zuckerman]

Yeah.

[Rose Rimler]

I talked about this with Faith in Madk. He's a professor in the nutrition and exercise department at the University of Copenhagen. And the first thing he told me was that, yes, your metabolism will get slower when you lose weight.

[Faith from University of Copenhagen]

When people lose weight, they burn fewer calories. And this happens both at rest and during exercise. And that is completely normal because a smaller body actually needs fewer calories to sustain its function.

[Wendy Zuckerman]

So it is true.

[Elena]

It is true.

[Wendy Zuckerman]

As you get smaller, your metabolism does slow down.

[Rose Rimler]

Yes. So basically what our metabolism is mostly doing is running a complicated machine. The size of that machine matters. If you're a bigger machine, you need more energy, you need more calories. If you're a smaller machine, fewer calories, less energy. And so as people lose weight, they have a smaller machine to run and they need fewer calories. And that in itself could be challenging to sort of dial down your calories more and more.

[Wendy Zuckerman]

All right, so then can we take it one step further? Because the Internet always does.

[Rose Rimler]

Yeah.

[Wendy Zuckerman]

If you then wait, cycle does over time that process, break that machine of ours and ultimately break your metabolism in some way.

[Rose Rimler]

So the people who talk about this, they often talk about this one particular study.

[John Rossi]

Let's talk about the Biggest Loser study.

[Faith from University of Copenhagen]

The Biggest Loser study.

[Rose Rimler]

It's the Biggest Loser study. The Biggest Loser. Remember that, Wendy?

[Wendy Zuckerman]

The reality show?

[Rose Rimler]

Yep. The reality weight loss competition.

[Sponsor/Ad Voice]

Uh huh.

[Wendy Zuckerman]

Yes, of course I remember it. Yelling. Lots of yelling at people.

[Rose Rimler]

Lots of yelling.

[Sponsor/Ad Voice]

Dan, no, I can't.

[Wendy Zuckerman]

Yes, you can.

[John Rossi]

Get back to work. Come on, Dina, come back.

[Wendy Zuckerman]

Dena, you're acting pathetic.

[Rose Rimler]

It was really intense. It had people do hours of exercise a day, like two or three hours a day while they were cutting calories as well. Significantly.

[Wendy Zuckerman]

It was mad. It was mad when you think about that moment in history.

[Rose Rimler]

And then.

[Wendy Zuckerman]

And then everyone would go for the. For the weight where they would measure themselves, and everyone would line up.

[Rose Rimler]

The public weigh in. The public weigh in?

[Wendy Zuckerman]

Yeah. So many people. And it was just, wow. Wow. Okay. We were doing that. Why are we talking about it on science first?

[Rose Rimler]

Because one good thing, interesting thing came

[Wendy Zuckerman]

out of that show.

[Elena]

Science.

[Rose Rimler]

We have some science from that show. Because one season, scientists actually followed contestants before and after they were on the show, measuring their resting metabolic rate. So they did that before they started the show, before they lost weight, and then after the show, when they had lost weight and they lost a lot of weight on average. This group of people, it was like 16 people. They lost about a third of their body weight on average.

[Sponsor/Ad Voice]

Wow.

[Wendy Zuckerman]

And so did their metabolism slow down as expected?

[Rose Rimler]

So it slowed down, of course, because they're smaller.

[Wendy Zuckerman]

Machines were smaller. But then the question is, when they. They put the weight back on, did they. What happened next?

[Rose Rimler]

They did. So over the course of six years, they. Most people put some of the weight back on or all of it back on. And the scientists circled back, they got back to them after these six years, and they measured their resting metabolism again. And so you would expect if the weight had come back, then the metabolism would bump up as well, right?

[Wendy Zuckerman]

That's right. So what happened?

[Rose Rimler]

They didn't find that these folks, their metabolism, on average, was still suppressed years

[Wendy Zuckerman]

later by how much?

[Rose Rimler]

Well, here's faith.

[Faith from University of Copenhagen]

So the resting metabolic rate was lower than predicted by about 500 calories per day.

[Wendy Zuckerman]

What is that in food?

[Rose Rimler]

It's a Big Mac.

[Wendy Zuckerman]

Okay.

[Alyssa Hasty]

Wow.

[Wendy Zuckerman]

A Big Mac a day. That's how much their metabolism had dropped on average.

[Rose Rimler]

Right. Meaning, like, next to someone who hadn't had this experience but was sort of the same size.

[Sponsor/Ad Voice]

Yeah.

[Rose Rimler]

That other person could eat a whole extra meal, essentially.

[Alyssa Hasty]

Yeah.

[Rose Rimler]

Per day than they could to stay the same.

[Wendy Zuckerman]

So it's weird.

[Elena]

It is true.

[Wendy Zuckerman]

It is true that weight cycling can mess up your metabolism.

[Rose Rimler]

Not so fast.

[Wendy Zuckerman]

Okay.

[Rose Rimler]

This is a weird study. It's small. What people did is quite extreme. We have other studies that are a little bit more in keeping with the reality of what Happens to most people and bigger, more people in the studies.

[Wendy Zuckerman]

Great. Yes. This was just 16 people. Right. Okay, so what else, what do other studies show?

[Rose Rimler]

Some studies do also find some effects, some like suppression of the metabolism.

[Wendy Zuckerman]

It's not just the biggest loser, but

[Rose Rimler]

the biggest loser found the biggest, most extreme result. Most of the studies find something much smaller. And in fact, a meta analysis found it was quite a small amount on average.

[Wendy Zuckerman]

The metabolism lowered by a small amount on average.

[Sponsor/Ad Voice]

Yeah.

[Rose Rimler]

And it's actually so small that Faithan argues that it actually could be within the margin of error for what these measurements can actually detect.

[Elena]

Aha.

[Wendy Zuckerman]

So this is good news for John, who's been weight cycling nine times.

[Rose Rimler]

Right.

[Wendy Zuckerman]

It suggests he, he hasn't broken his metabolism. Right.

[Rose Rimler]

Yeah, yeah. And I called him actually, and I, after we talked the first time, after I'd done some research, I called him back and I told him about some of the science here, including this metabolism finding.

[John Rossi]

I've been told by so many people my whole life that I, you know, that I am hurting myself and I am causing myself these, like, long term issues.

[Rose Rimler]

And from the weight going up and down.

[John Rossi]

Yeah, yeah. To the point where it has scared me to try losing weight sometimes. And I'm like, no, what if I'm doing more damage? And so that's, that's really encouraging.

[Rose Rimler]

Science to the rest. Science to the rescue. No, we're such nerds.

[Wendy Zuckerman]

I know.

[Rose Rimler]

It's nice because science doesn't always come to your rescue, you know, it does not. And sometimes it really kicks your ass.

[Expert/Researcher]

So.

[Wendy Zuckerman]

Okay, to. The next thing I want us to look into is what happens to your muscles when you lose weight and then put it back on and lose weight and put it back on. Because the way some people talk about it online, it's almost as if your muscles will disintegrate over time. Do you know what I mean? This whole Internet's so extreme. What is happening to your muscles?

[Rose Rimler]

Extreme. What people do say is that, you know, when you lose weight, you lose some of your muscle and then you, when you gain it back, you don't get the back the muscle or not as much, you get back more fat.

[Wendy Zuckerman]

Okay. Yeah, yeah, yeah.

[Rose Rimler]

And that can happen. So there is a study in North Carolina where researchers followed people who went through a weight cycle over about a year, lost weight, gained it back. They found that people lost 74% of the weight as fat, but when they gained weight back, 88% came back as fat.

[Wendy Zuckerman]

Right. But when it's not a huge difference, but it's definitely There, Right?

[Rose Rimler]

It's there.

[Sponsor/Ad Voice]

It's there.

[Wendy Zuckerman]

And you could imagine if you have that difference over time with weight cycling, you're going through this nine times. The fear would be that then it would compound and you would, with every weight cycle, lose more and more muscle. Is that what we see?

[Rose Rimler]

Well, not every study finds this, so. A very similar study. Oh, Raj, you've done it to me again. Look, you gotta read more than one

[Wendy Zuckerman]

study and you gotta tell me. All right, so what you guess? Okay, don't tell me.

[Rose Rimler]

Let me tell you about this other study.

[Wendy Zuckerman]

Yeah, tell me about the other study.

[Rose Rimler]

This one was from Germany.

[Sponsor/Ad Voice]

Okay.

[Rose Rimler]

Researchers similarly followed people when they lost weight and gained back. They gained pretty much the same amount of fat as they had initially lost. Same amount of muscle, no real difference. So what you might ask me is the difference between those two studies?

[Wendy Zuckerman]

Yes, that is what you might ask. I will ask you what is the difference between those two studies?

[Rose Rimler]

The difference was age. So in the study where people gained back more fat than they had lost, they were older. They were people in their 50s, 60s, and 70s. While in the study where people did not really see a difference, they gained back just as much muscle as they lost. They were younger, 20s, 30s, and 40s.

[Wendy Zuckerman]

And we know that over time, you. You lose muscle, we all lose muscle, whether we're going through weight cycling or not. That is just one of the inglorious.

[Rose Rimler]

Just happens to everybody of aging.

[Wendy Zuckerman]

Yes.

[Elena]

So.

[Wendy Zuckerman]

So this isn't such a big deal then, you think?

[Rose Rimler]

I mean, it's, It's.

[Caller/Listener]

That's.

[Rose Rimler]

This is a tough one because. And I have spoken to some researchers who are genuinely worried about this, so that's a legitimate concern. But the way people talk about this online, that you're, like, doomed to ruin your body composition. I didn't see any evidence that that's the case.

[Wendy Zuckerman]

Right.

[Rose Rimler]

But yeah, I mean, and then your question, Wendy, of like, does this compound? Like, does with each successive weight cycle, you lose more muscle, you gain more fat?

[Wendy Zuckerman]

Yes.

[Rose Rimler]

I can't really answer that because we don't really have those studies. We have very few studies that follow people for more than one weight cycle. And that's true for all of us. Mostly it's just one round of weight cycling.

[Wendy Zuckerman]

What did John think about this?

[Rose Rimler]

He, you know, John said he wasn't. This wasn't something he was actually that worried about, because from his own experience, he was like, no, I. When I lose and gain weight, it doesn't really affect. Doesn't seem to affect the way I can operate my body. Like he talks about being a drummer.

[John Rossi]

I trust my arms, whatever size I am. Like, I trust that my muscles will do the same thing. Yeah, so that does make sense. I wasn't too worried about that, but I mean, it's nice. Like I wasn't worried about it, but. But cool. I'll take it.

[Wendy Zuckerman]

All right, Rose, after the break, we're

[Rose Rimler]

gonna talk about, like, health more broadly. Inflammation, diabetes, heart disease. Does weight cycling make all of that worse?

[Wendy Zuckerman]

Coming up.

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[Wendy Zuckerman]

Welcome back. Today on the show we're talking about weight cycling or yo yo dieting. What happens to your body when you lose a bunch of weight and put it back on? Lose a bunch of weight and put it back on. The Internet says that this can over time make you sicker and sicker. And we're looking into that claim. And one idea that I really want to probe is around inflammation and that this weight cycling can ultimately increase the amount of inflammation in your body. Tell me the science, Rose.

[Rose Rimler]

This comes from what we know about fat tissue on our bodies. So, you know, you and I, Wendy, and maybe our audience probably assumes that fat, the fat on our bodies is, is inert. It's just like squishy stuff that's there to act as padding or maybe, you know, provide a little extra energy if we need it. And actually that's what scientists used to think too, until like the mid-90s when they started to realize that fat is actually a very active tissue in the body. And one of the ways it's active is that it's actually full of immune cells. I spoke about this with Alyssa Hasty. She is currently a professor at the University of Texas Southwestern Medical Center.

[Alyssa Hasty]

Every single immune cell that's known to immunologist exists in our fat.

[Rose Rimler]

This is especially true for the fat that collects around our organs, visceral fat,

[Wendy Zuckerman]

which you're probably familiar with, the more dangerous fat. That's the fat scientists are worried about.

[Rose Rimler]

Yeah, when fat collects around your organs, that's bad. And one reason is because that's not really a place where we're meant to store fat. It's like not set up. The body isn't really set up to support the fat there. And so there isn't really like good blood supply for those cells, those fat cells in that area. And so they get like stressed out, they don't get enough oxygen and they like malfunction and they even die. So then there are these white blood cells called macrophages that have to go in and clean up the debris from those dead and dying cells. But then they can get overwhelmed. So here's Alyssa.

[Alyssa Hasty]

And so they send out signals that say, hey, other immune cells, other macrophages Come help us out here. We've gotta take care of this debris, this dead cell.

[Wendy Zuckerman]

Aha. So then you get more, basically more and more inflammatory cells. Right. More and more macrophages, then calling out more and more immune cells to come and help, and you just get this kind of vicious cycle. But then the question for us today is, does that get worse if you lose weight and put it back?

[Rose Rimler]

Right. And so that's what Alyssa wanted to test. So she set up this mouse model where she had the mice gain weight by feeding them a high fat D9 weeks. Then she switched them to a low fat diet. Was that kind of. Is that like putting the mice on a crash diet?

[Alyssa Hasty]

Yeah, it definitely is.

[Wendy Zuckerman]

And then she yelled at them, like in the Biggest Loser.

[Rose Rimler]

Yeah. And she made them go round and round and round in their little hamster for hours and hours. Run, run and televised it.

[Wendy Zuckerman]

Yeah.

[Rose Rimler]

So then to have them go through, like a whole cycle, she had the mice, she put them back on a high fat diet for another nine weeks, they gained weight again, checked on their immune cells, and what she found, especially regarding this type of immune cell called the T cell, was surprising.

[Alyssa Hasty]

The T cells were elevated even further in the weight cycle compared to the obese, only despite the fact that they were the exact same weight and had the exact same visceral fat mass and total body adiposity.

[Rose Rimler]

So these were even more, like, agitated. The mice were worse off in terms of what their T cells were doing than the control mice, who had never weight cycled but had been obese basically the whole time.

[Wendy Zuckerman]

The immune cells didn't like it, the going back, the cycling.

[Sponsor/Ad Voice]

Aha.

[Rose Rimler]

And so this is how Alyssa puts it.

[Alyssa Hasty]

The body remembers, the immune system remembers our body weight and gains and losses in that.

[Wendy Zuckerman]

Uh huh. The body remembers how. What's going on there?

[Rose Rimler]

We don't totally understand all this, but it seems like something about this, like the stress of the weight loss, the weight gain, the weight loss is like turning on the immune system in a way that's hard to turn off. And that could be leading to some kind of chronic inflammation, which we know is bad for us in all kinds of ways.

[Wendy Zuckerman]

We said science isn't always your friend.

[Rose Rimler]

No.

[Wendy Zuckerman]

Do we know why this is happening? And obviously, this was just a study in mice. You're gonna now give me another study where they found something totally different? Well, I mean, wait, are you really gonna give me another study that found something different?

[Alyssa Hasty]

Rose?

[Rose Rimler]

Yes and no.

[Wendy Zuckerman]

Science tease.

[Rose Rimler]

So after looking at this study in mice, I wanted to look at studies in People.

[Wendy Zuckerman]

Thank you.

[Rose Rimler]

And I did find along these same lines, I did find studies that compare people who have weight cycled versus people who have not weight cycled. But they both started out at kind of the same weight.

[Wendy Zuckerman]

Yes, yes.

[Rose Rimler]

And were similar in other ways. And what those studies often find is that the weight cyclers have worse health outcomes than those who haven't weight cycled.

[Wendy Zuckerman]

In what way?

[Rose Rimler]

These studies have found a higher risk of heart failure and higher risk of death. Actually, a couple studies.

[Alyssa Hasty]

Wow.

[Rose Rimler]

So I don't want to leave things there, though. And the reason is, you know, those studies are not bad studies, but they can't answer some basic questions here. So, like, they're just observing what happens between one group and another. They can't say, like, weight cycling cause people to be. To die or to get heart failure.

[Wendy Zuckerman]

Got it, Got it. We need a different kind of study for that. A randomized, sometimes we don't have control trial anything else. Yes.

[Rose Rimler]

Yeah, but.

[Wendy Zuckerman]

But in this case, we do.

[Rose Rimler]

We have some randomized controlled trials that can help us.

[Wendy Zuckerman]

Uhhuh. Tell me about it.

[Rose Rimler]

So I talked about this with Jamie Hartman Boyce. She is an associate professor of health policy and management at the University of Massachusetts Amherst. And she wrote a review paper looking at studies where people lost and then regained weight after going through what are called supervised weight loss programs.

[Expert/Researcher]

Eating a bit less, you're at a calorie deficit, and you're exercising more. So we're not looking at people who are like, on a juice cleanse six weeks. Yeah.

[Rose Rimler]

We're looking at people who are, like,

[Expert/Researcher]

eating more vegetables and moving their bodies more.

[Rose Rimler]

So Jamie's question was, how does the health of these people who have lost weight in this healthy way, gained much of it back? How does it compare to people who have never lost weight? Who are the control groups?

[Caller/Listener]

Yeah.

[Wendy Zuckerman]

Great.

[Expert/Researcher]

And one of the things we found was that even if you regained the weight back. Right. So even if you started a certain weight, you did your diet and exercise program, you stopped it, you went back to your starting weight. Compared to someone who had stayed at a stable weight the whole time and not done that program, you were still less likely to get type 2 diabetes.

[Rose Rimler]

And it wasn't just diabetes. It was also lower cholesterol and lower blood pressure.

[Wendy Zuckerman]

Why was weight cycling healthy? In this case, it seems like it

[Rose Rimler]

could come down to how people lost the weight. Making healthy changes, getting a little more exercise, eating more vegetables. Even if people aren't able to keep up those new habits forever, the period of time where they were doing Those healthy habits which resulted in weight loss, that's what was good for them. But these other studies, we don't know how or why they lost the weight. And then with the mice, you know, it was like a crash diet. This was like healthy changes resulting in weight loss.

[Wendy Zuckerman]

So is it even about the weight loss at all?

[Rose Rimler]

All or.

[Wendy Zuckerman]

It's just that for a portion of the study, these people were eating lots of vegetables, moving their bodies, and that's what was good for them, whether or not they lost weight or not.

[Rose Rimler]

That's one. Yeah, I think that's a fair interpretation. I mean, there's a lot of nuance here, but it, it does make sense if you think about, if you know the broader literature about weight and health. So there's a study I love, it's a big survey, like 12,000 people are in it. They asked about healthy habits. So like how much fruit and veg do you eat? Do you exercise regularly? Smoking, drinking?

[Wendy Zuckerman]

And these were people of all kinds of weights.

[Rose Rimler]

Yes, all kinds of weights. And they tracked them over time and what they were measuring was all cause mortality. So like that's the big one. Like are you more likely to die? They found that the thing that mattered the most for, you know, death was not your weight, but the healthy habits that you did. So if you were someone who your BMI technically puts you as obese, but you have all these healthy habits, you were just as likely to not die as a person whose BMI was normal and did those healthy habits.

[Wendy Zuckerman]

What these studies are suggesting is if you're doing healthy things, that's the key.

[Rose Rimler]

Yes. And you have a lot more control over that than you have of your body size. So it makes more sense to focus on that. And, and that's what Jamie said as well.

[Expert/Researcher]

So I think the data is very clear that if like what we're trying to do is improve our health and well being. Right. Then you know, if we eat healthier, we exercise more, regardless of what happens to our weight. And one of those things that can happen is that we lose weight and regain it. We are doing something good for ourselves.

[Rose Rimler]

Okay.

[Expert/Researcher]

And for the people who love us, who want us to stick around for longer.

[Rose Rimler]

So when I told John that it's, it's the healthy behaviors more than the weight that really matters, this is what he said.

[John Rossi]

Wow, that's really cool. That's great science.

[Wendy Zuckerman]

Back to being your friend.

[Rose Rimler]

But it was also, there's something, I think about it that was slightly annoying to John because it made him think of like all the bull he's had to sort through. And all the people saying, like, oh, if you, if your weight fluctuates a lot, you're going to really harm your health.

[John Rossi]

Those beliefs have been so common and so repeated over and over and over again that it shows me that, you know, people don't know what they're talking about with this stuff all the time. And it's another nice reminder to not let other people shape me in a literal sense in this case, and that I should. I should worry more about, you know, what I think and what the science says than what people tell you, you know.

[Wendy Zuckerman]

So what does this mean for that fabulous pink outfit that John's got?

[Rose Rimler]

I did ask.

[Wendy Zuckerman]

Did you? Yeah.

[Rose Rimler]

You said your confident, wacky outfit was like. I think you said it was like. Was it hot pink?

[Elena]

Yeah.

[John Rossi]

Oh, my gosh. So much hot pink.

[Rose Rimler]

And skinny jeans.

[Elena]

Yep.

[Rose Rimler]

Reflecting on that, it strikes me as a very early 2000s outfit. So what would the. Let's say you get that burst of confidence and creativity and you want to express yourself through wacky dress. What does the 2026 version of that look like?

[John Rossi]

Well, 100% goofy animal shirts, always. I just, I love animals so much now and probably still skinny jeans because I don't care if they're in style or not. My boat looked great in those jeans.

[Wendy Zuckerman]

That's Science Versus. Thanks, Rose. How many citations are in this week's episode?

[Rose Rimler]

This week there are 66.

[Wendy Zuckerman]

66. And if people want to see them in all their glory, where can they go?

[Rose Rimler]

Check out the transcript to find that link to the transcript in our show notes.

[Wendy Zuckerman]

Thanks, Rose.

[Rose Rimler]

Thanks, Wendy.

[Wendy Zuckerman]

This episode was produced by Rose Rimler with help from Maketti Foster Keys, Meryl Horne, and Michelle Dang. Wendy Zuckerman, that's me, is our executive producer. We're edited by Blythe Terrell. Fact checking by Diane Kelly Mix sound design and video editing by Bobby Lord. Music written by Bobby Lord. Bumi Hidaka. So Wiley, Emma Munger and Peter Leonard. Thank you so much to all of the experts that we spoke to for this, including Dr. Heidi Silva and Dr. Andrea Rossi. A special thanks to Jennifer C. Wolf and Sasha Voroshenko. A big, big thanks to all of the folks who called in to tell us about their weight cycling experiences. Thank you so much. It means so much to us that you trust us to tell us your stories, so thank you so much. Science Versus is a Spotify Studios original, so listen to us for free on Spotify or wherever you get your podcasts. We're all over. We're on YouTube.

[Expert/Researcher]

We're on Apple.

[Wendy Zuckerman]

If there's podcasts there, so are we. Like and subscribe, follow, do all that stuff and get in touch with us. We're also on TikTok and Instagram. All the ways to get in touch are in the show. Notes. I'm Wendy Zuckerman. Back to you next time.

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