IRA FLATOW: This is Science Friday. I’m Ira Flatow.

If you’ve ever watched the reality TV show The Biggest Loser, you know that those contestants put in a gargantuan effort to lose weight. They diet rigorously, they exercise for many hours a day, and they compete with each other to completely change their bodies. And many do change their bodies, some losing 100, 200, or more pounds in a very short period of time.

But what happens after the cameras, the coaches, and the cuisine pack up? It turns out that like many people who lose weight, maintaining that smaller frame is hard even for those who were so successful at achieving it in the first place. Now a new study of the show contestants has found that most of them have gained weight in the six years since and some of them had gained back most or even all of what they lost.

And what surprised the researchers though is this– that while a drop in metabolism after the initial weight loss was expected, every participant’s metabolism remained much slower than it should be for someone their size, despite the passage of time. So what’s going on here? Does the body want to return to its former weight? What does this mean for anyone who’s unhappy with their current weight? And what does this mean for the hard emotional work put in by The Biggest Loser contestants themselves?

We’re going to discuss it and take your stories. If you’d like to give us your battle with weight, what’s going on with you, whether you lose or you maintain it, what has the process been like, was it worth the effort, our number is 844-724-8255. You can also tweet us @scifri.

Let me introduce my guest. Kevin Hall is a researcher with the NIH’s National Institute of Diabetes and Digestive and Kidney Disease. He is the lead author of the study which appeared in Obesity earlier this week. Welcome to Science Friday, Doctor Hall.

KEVIN HALL: Thanks for having me.

IRA FLATOW: Dina Mercado was a contestant in the show’s eight season and a participant in Doctor Hall’s study. Welcome to Science Friday, Dina.

DINA MERCADO: Thank you for having me also.

IRA FLATOW: You’re welcome. Doctor Hall, how much reality television do you watch anyway?

KEVIN HALL: My wife doesn’t like how much reality TV I watch. But in this case, maybe it actually worked out for the benefit of science.

IRA FLATOW: So what gave you the idea to study the contestants on The Biggest Loser?

KEVIN HALL: Right. Well actually, I came home from the lab late one night, turned on the television, and saw people stepping on scales at the end of a previous season of The Biggest Loser. And I couldn’t believe how much weight they were losing– it was dramatic amounts. And so this was my field of study and I figured I should be able to understand what’s going on.

And so I eventually contacted the physician in charge of their care at The Biggest Loser and started chatting with them about, well, what’s happening to these folks’ metabolism. How much fat are they losing versus lean tissue? And these kinds of questions. And we basically collaborated initially on a study that was published several years ago about what was happening to their metabolic rate and their body composition as they lost weight. And now six years later we did this follow-up study on 14 of the 16 original subjects.

IRA FLATOW: So you followed-up with them six years after they lost weight. And what did you discover?

KEVIN HALL: Yeah. So as you mentioned in the introduction, we were very surprised by the fact that despite regaining a substantial quantity of the weight that they’d lost, their resting metabolic rate– that’s the number of calories their body is burning in order to just basically maintain life– we’re still at this very low level that we observed at the end of the weight loss period on average, and much less– about 500 calories a day less– than would be expected for their newer, slightly higher body size. So this means that they’re at some sort of disadvantage in terms of trying to keep the weight off.

And so we weren’t that surprised that folks would regain the weight. We expected that most people who lose a lot of weight will regain some of it back. But what we were most surprised by was the persistent slowing of metabolism that was observed in these folks.

IRA FLATOW: And you have no idea why that would continue?

KEVIN HALL: Yeah. We don’t know if it was something that was a result of this rapid weight loss that they experienced early on as part of the competition. What we do know is that everybody experiences the metabolic slowing to some extent when they tried to lose weight, especially in the early time period. And what we think that we’re able to show here is just how strong that can be when you look at extreme weight loss like these folks have experienced. I don’t think that everyday folks will experience either this extreme amount of weight loss or this metabolic slowdown that these folks experienced in a quantitative sense, but they will experience it to a smaller degree.

IRA FLATOW: Dina, what did you do during the show to lose so much weight so quickly? You lost 75 pounds?

DINA MERCADO: Actually, it was 80.

IRA FLATOW: 80? How much work did that take? Describe for us.

DINA MERCADO: Oh, a whole lot of work. A typical person goes to work for an eight hour day. And just like that, that was our job. And we worked out from eight to nine hours a day just overall with the trainer. And they would leave us homework and we’d continue to work out. And then meals in between, of course, and snacks in between, of course. But at the end of the day, you still wanted to work out even half those eight hours and nine hours because of the fact that it was still a game and you wanted to do more than the next person that was sitting next to you or so on and so forth. So it was about, I want to say, 9 to 10 hours a day, depending on your personal preference, just to stay that week longer.

IRA FLATOW: Wow. And so when your weight returned, you must have been devastated.

DINA MERCADO: Absolutely. You don’t do that to gain weight back. And so as it started to crawl on, it was just like what’s going on?

I was able to maintain for a little while, for about two years. I did become pregnant after a while, but I was able to get a lot of that off. And then I got pregnant again. And at that point that’s where I began to see things change.

Because even though I was doing what I did the first time to begin to lose, the second time, after that second pregnancy, I was doing the same thing to try to get back down to that weight that I had maintained after my finale and it wasn’t working the same. And it was just like, wait a minute, why did it work at one point and now it’s not working anymore? And so that’s where I’m at. And all this makes sense now, because it’s like, wow, I didn’t realize that I had to burn that many more calories on top of what I was doing when it worked previously before.

IRA FLATOW: Because your metabolism slowed down.

DINA MERCADO: Correct. And I didn’t realize that. I didn’t know that. So it makes sense.

So when we did the study and Doctor Hall came out these results, it was like, wow, I get it. Now that I know what I know, I can begin to adjust either what I put in my mouth and my intake or adjust just working out even more to be able to get back, or to try to lose again, or even try to maintain what I have at this point.

IRA FLATOW: So you could eat less, fewer calories, and still not take the weight off.

DINA MERCADO: Well, that’s where we’re at. I guess at this point I’m trying to stay between the 1400, 1500 calories. And now I like I have to drop. But at the same time, if I drop another 500 calories, I’m almost eating nothing.

IRA FLATOW: Right.

DINA MERCADO: So it’s either I have to do that to try to either lose or even maintain, or I have to just work out more or be more active than what I am right now. And to be quite honest with you, with two little ones and trying to get to the gym at least three times a week and whatnot, it’s difficult. It’s difficult to do that. But at the same time, I don’t want to see this number go up anymore.

IRA FLATOW: Yeah. Doctor Hall, as someone who works out a little bit– and I know I’m trying to maintain my muscle mass as I get older– the rule of thumb has always been, well, if you work out, you’re going to build up more muscle. And more muscle will more efficiently burn calories. Did that not happen here?

KEVIN HALL: Yeah. So that’s an interesting point. And this is a bit of mythology that’s our original study busted, actually. Because these folks who are doing tons of exercise, an unsustainable amount of exercise, during their weight loss competition, were actually able to maintain their lean body mass and their muscle much better than would be expected for the amount of weight that they lost. In fact, one of the things that we did was we compared those folks with people who lost weight, a similar amount of weight, by another means, which is one of these bariatric surgery. And they lost quite a bit of muscle.

The surprising thing was that despite that preservation of muscle, their metabolic rate slowed down much more than would be expected, several calories a day more than would be expected. And in hindsight, when you actually look at the physiology of muscle, muscle actually doesn’t burn that many calories at rest. We’re talking about 15 calories per day for every kilogram of muscle– so that’s 2.2 pounds of muscle. And people don’t generally change their muscle by more than a kilogram or so when you’re trying to work out and gain weight, unless you’re a bodybuilder. And even then, it’s not that many calories at rest. So that’s a little bit of mythology that still persists out there in the exercise and fitness communities.

IRA FLATOW: There are some scientists, like Robert Lustig, who have suggested that the body has a set weight that it wants to stick to. And the brain and the metabolism will make adjustments, whenever you do, to go to that weight where it wants to be. Do you agree with that research?

KEVIN HALL: We found some evidence for that in these particular subjects, actually. So for example, one of the perhaps counter-intuitive findings that we obtained was that the people who had actually had the most success at maintaining the weight loss were the folks who actually were experiencing the greatest metabolic slowing. So they were burning the fewest number of calories.

And the way we like to think about it is that the body is behaving like a spring. And you can pull on the spring and intervene by dieting and exercising, and you’re able to stretch the spring out and analogously lose weight, but the harder the spring is going to pull back on you. And so the folks who are most successful are pulling the hardest on the spring and stretching it out the most, but they’re also ones that are experiencing the greatest pullback. And so that goes along with what you’re saying, that the body has a preferred weight that it would like to maintain and your efforts to change from that weight are met with some resistance.

IRA FLATOW: Let’s see if we can go to the phones right now. Got a couple of calls in. Let’s go to Beaufort, South Carolina and Todd. Hi, welcome to Science Friday.

TODD: Thank you.

IRA FLATOW: Hi there. Go ahead.

TODD: Two years ago September, I had one of the bariatric surgeries. And I was able to go from well over 330 pounds to about 115 pounds. And you get, they say, a honeymoon period of about a year where you don’t have much of an appetite. But at about a calendar year, your appetite goes back. And it’s been a real fight to keep the weight off.

IRA FLATOW: Yeah. Bariatric surgery, Doctor Hall?

KEVIN HALL: Yeah. So the caller mentions bariatric surgery. And I mentioned previously that folks who undergo bariatric surgery, unless they also do some exercise or change their diet in some way to perhaps increase protein intake, will lose some of this lean mass, which will tend to slow metabolism.

But one of the interesting things that we found when we compared matched bariatric surgery subjects with The Biggest Loser contestants was that they also experienced the metabolic slowing within the first year. But after that, very interestingly, that greater-than-expected change in metabolic rate went away. In other words, their metabolism normalized after a year of bariatric surgery. But that was obviously not the case in The Biggest Loser contestants. There might be some sort of resetting of the quote unquote “set points” with some of these bariatric surgeries.

But the caller is right. Your appetite will also go up over time. And you will eat more food following the initial stages of the bariatric surgery. But what we know is that right now those are the only persistent, long-term, reproducible kinds of interventions that we can do to lead to long-term weight loss in people. And we’re really trying to understand the biology of what’s responsible for the relative success of bariatric surgery compared to the lifestyle interventions that we’re all familiar with.

IRA FLATOW: This is Science Friday from PRI, Public Radio International. I’m Ira Flatow talking with Kevin Hall, who is a lead author of a study which appeared in Obesity earlier this week and with Tina Mercado, who was a contestant in the show’s eighth season and a participant in Doctor Hall’s study. Tina, are you sorry now after all this? Are you sorry for going on the program now that you lost the weight and it seems like a nightmare trying to keep it off?

DINA MERCADO: It’s pretty discouraging; that’s the truth. However, I can’t really regret doing this whole thing. And the reason I say that, and pretty much the only reason I say that, is because I initially went on The Biggest Loser to be healthy, of course. And in becoming healthy I wanted to bear more children. And I have had two children, I would like to say, because of the weight that I’ve lost. And so I can’t completely regret doing what I’m doing.

However, what I will say is if somebody came up to me, or called me, or whatever and asked me my opinion on being the next contestant possibly on another season or so, I would strongly discourage them to do so, knowing the findings now. And so that’s where I sit with it. I sat and thought about it. And I said I can’t regret it at this point. Now I am where I am. I do have three children all together now.

And now what’s next for me and what can I do to either try to find a way for us to the reverse what’s going, on or to just obviously burn less calories, or eat less, or figure something out? Because like I said, that’s my biggest fear, is what’s my metabolism going to do, where am I going to be at in five years, 10 years, 15 years from now? And so that’s where I sit with it. And it’s just what can I change at this point that I’m here. I can’t go backward, obviously. And so now it’s just trying to figure out what to do now.

IRA FLATOW: Doctor Hall, there’s a growing movement by activists who emphasize health at any size and encouraging people to focus on healthy habits without regard for the numbers on the scale. Do you agree with this philosophy?

KEVIN HALL: You know, I do in the following sense. I think a lot of people conflate the cosmetics of weight loss with the health benefits. You don’t actually have to lose The Biggest Loser style amounts of weight in order to improve your health.

And in fact, one of the things that I would stress is very important for people to come away with is a message for not necessarily targeting these very unrealistic an unsustainable amounts of weight loss. If you can change your diet, and eat healthier foods, and add some exercise in your life– not crazy amounts like The Biggest Loser does on the program– you’re going to see independent health benefits regardless of your weight. And if you make those changes and make them in a sustainable way, a way that you can actually keep them and integrate them within your life over the long term, your weight will settle at a different value or it might not settle at a different value, but regardless your health will be improved.

IRA FLATOW: Well, interesting stories. Dina, thank you for sharing that with us and your trials. And we wish you all the best of luck.

DINA MERCADO: Thank you so much. I appreciate that.

IRA FLATOW: Dina Mercado is a former contestant on The Biggest Loser and a participant in Doctor Kevin Hall’s study. He’s a researcher at NIH’s National Institute of Diabetes and Digestive and Kidney Disease and the author of this study on the physiology of weight loss and maintenance. Thank you Doctor Hall for joining us also.

KEVIN HALL: Thanks for having me.

Copyright © 2016 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of ScienceFriday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies.