Leah:

Hello and welcome to the Ideal Nutrition Podcast. I am Leah Higl and I am here with my co-host Aidan Muir and today’s episode is going to be focused on a study titled, “Persistent Metabolic Adaptation Six Years After the Biggest Loser Competition”. Or the Biggest Loser Study as we will refer to it in this podcast. This was from 2016.

This study was done on participants from Season 8 of The Biggest Loser, which was aired in 2009. So, you know, just a few years ago at this point. We’ll also touch on aspects of a follow-up study from 2022 titled “Energy, Compensation and Metabolic Adaptation, the Biggest Loser Study Reinterpreted”.

We want to cover this because, I mean, even if you just think about the Biggest Loser in general, like how crazy and insane that was, what they were like had those participants doing, it’s just kind of crazy. And then for us to kind of have some of this data in the form of a study is pretty cool. Because it was such a novel thing, there was some pretty novel and interesting findings as part of this study and we just really want to unpack it.

Aidan:

So talking about the study of the 16 participants in the competition, 14 agreed to the follow up study, which I think is a pretty high retention rate considering the nature of the show and stuff like that. RMR, so resting metabolic rate was measured using indirect calorimetry at the baseline so when they first started at the 30 week mark at the competition, and then also six years later.

For what it’s worth, even if you’re listening to this, you would not have actually needed to see the show. You obviously understand what the show is about and everything like that. So even if you don’t fully know the intricacies of the competition, you’ll still understand this episode.

So anyway, they defined metabolic adaptation as the difference between their actual resting metabolic rate and what a formula would predict. Because prior to the competition, their resting metabolic rate or RMR was roughly what a formula would have predicted it to be. So anyway, during the competition, on average participants lost 58.3 kilos. It’s crazy.

Leah”

Huge, absolutely huge.

Aidan:

Massive. Which is part of why all of this is so interesting. Not what we’d recommend, but interesting. On average, they regained 41 kilos over the six years. Even that’s little bit of an interesting point. Like anytime I mentioned the biggest loser, even though I’m big on that, we would never recommend that. A lot of people instantly are like, yeah, they regained all the weight like after a show. Six years later, they were 41 kilos on the regain journey, a little thing worth contemplating is irrelevant to what we’re about.

But a little thing worth contemplating is like, if they had never done the show, where would they have been six years after? Many things to contemplate in all of this, but I would assume they would have been heavier. that’s just another little thing to chuck in here, unrelated to what we’re talking about. But I don’t want to sound like I’m pro Biggest Loser here. Sorry.

But going through it. So anyway, let’s get into what we’re actually talking about. Prior to the competition, their resting metabolic rate was what you would predict. After the competition and six years later, it was around 500 calories lower than a formula would predict.

Leah:

So our interpretations of that, because it is a little bit of a wild finding, like in seeing that data, you could probably start to interpret it as a resting metabolic rate that is 500 calories lower than what would be predicted with an equation could basically be like the equivalent of perpetually dieting with a 500 calorie per day deficit, just to simply maintain your weight. It is worth acknowledging that the participants RMR was still averaging around that 1900 calorie amount. It’s just that if we heat it all into an equation, like the prediction would be closer to 2,400 calories. So there was like that huge 500 calorie discrepancy there.

And many people in the fitness industry interpreted this as a bit of a sign of metabolic damage, particularly occurring when there was kind of like this crash dieting that had occurred. And then that being kind of a long lasting effect of this quote on quote crash dieting.

Aidan:

Even at the time when this came out, I remember working with clients who were reportedly on quite low calorie intake. And I was kind of wondering, I was like, is that what’s happening here? But interestingly, pretty much every other study looking at metabolic adaptation finds that reverses when calories are ranged. Usually it doesn’t take that long either. takes like on average, if you measure around four weeks later after a fat loss phase has ended and you’re on higher calories, usually metabolic adaptation is non-existent based on what the research has found. I don’t think it’s a hot take to make the argument that bigger slash longer weight losses might take longer to return to the baseline.

But taking one moment here with this specific study, the participants averaged a small to moderate surplus for six years. That’s very, very different. Based on the logic of metabolic adaptation, if you were in a small to moderate surplus for six years, you would assume it would be going in the other direction. But either way, no matter how we look at it, this study is a huge outlier.

Leah:

Yeah. And there are a few ways we can start to maybe explain why this is such an outlier study. One explanation that people have highlighted is the rate and volume of weight loss in such a short period of time and that potentially playing a role. It was extremely rapid. It involved kind of major caloric restriction and a fair bit of over-exercising. So in that way, it was pretty novel compared to how most people, I guess, go about a weight loss journey.

Aidan:

Yeah, there’d be literally no other study looking at anything.

Leah:

Yeah, that would be crazy to put a study together like doing that to people.

But whilst there isn’t as much research as we’d like looking at metabolic rate alongside things like bariatric surgery, where we would see potentially like a very similar like….

Aidan:

Rate of weight loss, large weight loss.

Leah:

Yeah, in like a short period of time. So it’s like, it would be potentially like a similar thing, but even looking at that research, it’s like when we’re not really seeing this kind of huge decrease in resting metabolic rate, like years down the line. And if this was the case, like if it was just the rate and volume of weight loss in that period of time, having this impact, we would see very similar results in people that had lost a lot of weight very fast from bariatric surgery.

Sure, there might be some key differences there, but it’s somewhat comparable. I guess something else to note is the Biggest Loser study participants also retained fat-free mass exceptionally well due to the large amount of exercise they were doing. I guess, in comparison to bariatric surgery, that may also be a key difference.

Aidan:

Yeah. Arguably I use ChatGPT too often, not for like serious nutrition stuff, but just like general like screening questions. And like even in the process of like putting together this podcast, like ask a bunch of questions, like for example, with the bariatric surgery stuff, I was like, hey, what studies exist on this topic? So I was like looking at stuff like that in addition to stuff that I’ve already previously read.

And it’s just a quick way of me looking for stuff. But one of the things I did put into ChatGPT was like trying to explain why in the Biggest Loser study, beyond my thoughts, like why there might’ve been this reduction, just to get multiple perspectives. And one of the things that it proposed originally was that due to the rate of weight loss, there could have been a large drop in fat-free mass. But when you actually do look at the data, they did retain fat-free mass like surprisingly well, like given the rate of weight loss, but like that massive amount of exercise and a bit of an emphasis on protein still clearly made a difference though. That wouldn’t explain the metabolism or the metabolic damage side of things.

But now let’s talk about the follow-up study from Kevin Hall, who was one of the original authors. So he did a bit of a narrative review in 2021 slash 2022, trying to explain why this was such an outlier. Because since that moment, like obviously a lot of research had come out. In this paper, a few things were brought up. The first one, was he, he discussed how the data had been misinterpreted as evidence that diets destroy your metabolism and most lifestyle interventions are doomed to fail. Even though the participants in the study still had a meaningfully clinical average weight loss of 12% after six years. That was everywhere. And honestly, even now in 2024, I still see people doing that. Like they will talk about if they use the line “diets damage metabolism.”

This is the study I see cited super often, because it fits the narrative, even if we were to ignore absolutely everything else and just focus on the fact that it’s still an outlier in terms of the massive weight loss and stuff like that. So that was a thing that was massively around. So he kind of highlighted it, kind of poked a hole a little bit in that. But now let’s talk about the stuff we’re actually meant to be talking about where the next thing is that he highlighted that the high physical activity could lead to a reduction in energy expenditure elsewhere.

This is known as the constrained energy expenditure model. Getting a little bit deep here, but like alot of this stems from work from a guy named Herman Poncer, who has done a lot of work with tribes such as the Hudsa and stuff like that, where even though they’re like hunter-gatherers and they’re physically active, their total energy expenditure isn’t quite as high as what you’d expect.

There are so many angles that we could look at this in terms of, let’s say people increase, let’s say somebody runs a marathon and let’s say, I don’t want to butch this, say they burnt like 2,200 calories just as a number. In our head, we picture it being like, okay, they normally burn this amount of calories. Now they’ve burnt 2,200 on top of that. If you think about that for half a second, you realise that that’s obviously not true. If somebody ran a marathon, what are they doing for the rest of day? Probably not moving at all.

So like the total daily energy expenditure is going to decrease. But the thing is that total daily energy expenditure wasn’t what was measured in this metabolic damage thing, what they’re measuring was resting metabolic rate. Let’s go back to that marathon example, still. If somebody had really high energy expenditure, like let’s use that marathon thing, is the body going to down regulate anywhere else? Is it going to decrease metabolic rate a little bit to conserve calorie expenditure because it’s so high elsewhere? And we have a lot of evidence that that happens.

Like we have evidence from the constrained energy expansion model. We have evidence with the low energy availability type space where like, as an example, a woman might lose her period to kind of conserve energy if they’re in a state of low energy availability. There’s so many things going on there.

It’s complex because I’m like, does the constrained energy expenditure model, does it actually account for all of this 500 calorie difference? Like, I don’t know if I personally go that far. But a few things that were pointed out in this was that the participants who had the highest physical activity six years later, also experienced the most measurable decreases in RMR. If we went just with the metabolic adaptation slash metabolic damage type of model, like we would think they’re the most metabolically damaged or adapted.

If we went with their constrained energy expenditure, it’s just like, they’re doing heaps of exercise down regulate somewhere else. And although I haven’t touched on it, these participants are still doing a lot of exercise on average. And there were some who were doing, I know, at least one hour per day, if not two hours at times as well.

Leah:

I think overall, it is a very interesting study with very novel results, but arguably the nutrition and fitness world would be much simpler if this study just didn’t exist. And it just comes down to it being a huge outlier compared to the rest of the research in this space. And trying to take useful information without awareness of all these kinds of complexities and the other research can lead to massive misinterpretations, which Aidan and I have both definitely seen online when people have kind of taken this data and used it to prove maybe a point they’d already had in their mind.

The constrained energy expenditure model could explain these findings to a certain extent, but even if that doesn’t fully cover it, I guess it wouldn’t read too much into this. And just in general, like it’s a novel finding, it’s a cool study, but I’m not basing my entire ideas around this concept on this study alone, obviously.

Aidan:

100% fully agree with that.

This has been episode 174 of the Ideal Nutrition Podcast. As always, if you have not already, if you could please leave a positive rating or review, that would be massively appreciated.