Podcast Episode 13 Transcript – Metabolic Adaptation

The Ideal Nutrition Podcast

Leah

00:00:05 – 00:00:22

Welcome to the ideal nutrition podcast. I am Leah Higl, and I’m here with my co host, Aidan Muir and today we’re talking about metabolic adaptation, otherwise known as adaptive thermogenesis. 

Aidan

00:00:22 – 00:01:18

So metabolic adaptation or adaptive thermogenesis, depending on which you prefer to call it like in the research, is typically called adaptive thermogenesis. I prefer to call it metabolic adaptation because it seems easier to understand that way. And it’s basically the phenomenon where, when dieting or adaptive thermogenesis is defined as when dieting, when your calorie expenditure drops by more than a formula would predict, sometimes people specifically refer to it as when your metabolism, the metabolism, drops by more than a formula to predict. I like the terminology metabolic adaptation, because it makes it easy to understand that it goes in both directions. It isn’t just something that happens while dieting. It actually happens in reverse, which leads us into a bit of a topic of like, what’s the difference between metabolic adaptation and starvation mode?

Aidan

00:01:18 – 00:02:01

to jump straight to the chase like, I don’t think starvation mode is a thing. It’s a thing that’s based on a grain of truth. But it isn’t a thing by itself. Um, what I mean by that is starvation mode is the concept of where you go so low in calories that your body starts to hold onto fat and try and prevent any form of fat loss and everything like that. The grain of truth is that metabolic adaptation does occur like your calorie expenditure tries to to decrease your body’s trying to conserve calories. It starts to down regulate a few processes that reduces calorie expenditure, and that makes it harder to lose weight. So that’s the difference between like, I suppose what they call starvation mode and metabolic adaptation. 

Aidan 

00:02:01 – 00:02:24

There was a concept that was popularised 5 to 10 years ago. Layne Norton was one of the biggest popularises of it. He has changed his stance, but he talked about a concept called metabolic damage, which is a phenomenon where, even years after chronic dieting, TDEE,. So total daily energy expenditure is still way lower than you’d expect. Um, did you ever see the biggest loser study? 

Leah

00:02:24 – 00:02:30

I have briefly seen it, but I have to say that I’ve learned a lot more about it since talking with you. 

Aidan

00:02:30 – 00:03:06

Yeah. So the biggest loser study is like the biggest example of this. It shaped my thought process about five years ago. The biggest loser study is about 10 participants. I think it was based on the 1st ever series of the biggest loser in the USA, and they measured their metabolic rate at the start, and they measured it five years later and on average, as most people would predict and already kind of be aware of. On average, they regained weight to roughly their starting point, even though they had this dramatic weight loss at the start. 

Aidan

00:03:07 – 00:03:51

That’s on average. Some people actually did maintain most, if not all, of their weight loss. That therefore also means some people went significantly further than their original weight. But on average, their basal metabolic rate was 500 calories slower than you would have predicted with a formula, even though it was 100% in line with what you would’ve predicted with a formula to start, which is insane. The empathetic approach I often take when thinking about that is a 500 calorie deficit is about half kilo per week. Weight loss. So it’s kind of like if your metabolism was 500 calories slower, it’s like you’re perpetually dieting at that kind of rate just to maintain your weight. Obviously, they still had really high BMRs. BMR, I believe, was over 2000 calories per day still, because they were quite large. 

Aidan

00:03:52 – 00:04:27

But it is an interesting concept. It’s like, hey, that looks like there’s lasting damage five years later because they did this extreme diet at one stage. Is that relevant for the average person, though? And that’s the big question, because that is, honestly, the only study I’m aware of where it was lasting metabolic damage, so to speak. And that’s why metabolic damage gained popularity because everybody was talking about this study. It was a really popular one because, like everyone could identify with the show as well. Like it was, it was like in pop culture as well. It wasn’t just this random research study, but that creates other issues where it’s like, it only had 10 people.

Aidan

00:04:28 – 00:04:47

who like, I’m not going to question this. But like, who’s to say they didn’t inaccurately measure anything as well? Like, who’s to say that? Like if one study shows something and every other study on the topic shows the opposite, who’s to say they didn’t inaccurately measure it? I’m not going to assume that they did, but that is a thought that pops in my mind. But then the other thing is they go through something extreme that nobody else goes through. 

Aidan

00:04:48 – 00:05:20

Nobody else loses weight the way they did during the biggest loser, like some people do, but like they did extreme amounts of exercise very, very, very low calories. They lost weight like crazy very quickly. They were trying to do it as quickly as possible. The only situation that can really see that is kind of relevant, is bariatric surgery. But even those people are not doing extreme levels of exercise. So even if their example was something that happens under those circumstances is not relevant for the average person. So that’s why I like the terminology metabolic adaptation more than metabolic damage or starvation mode because metabolic adaptation reverses when you go on to higher calories. 

Leah

00:05:20 – 00:06:10

So to really understand metabolic adaptation, I think it’s really good to understand the components of your total daily energy expenditure and what physiological processes actually occur. With metabolic adaptation and how our calorie intake can affect that. And what aspects of that it does affect so breaking our total daily energy expenditure down into, um, the four kind of sub components of it. So you’ve got your largest user of energy, which is basal metabolic rate, which is basically the calories you burn at rest. So that’s mainly influenced by your body weight, your body composition. And when we’re talking about metabolic adaptation, we’re mainly talking about the effect that your calorie intake has on your basal metabolic rate or your BMR.

Leah

00:06:10 – 00:06:53

It is just in regards to the energy availability in your total system. But there are a few other subcategories that are at play when we’re talking about total daily energy expenditure. So we do have neat, otherwise known as non exercise activity thermogenesis. I always find these such a tongue twister. Hence why I always call it NEAT instead. Um, but that’s what it stands for. Um, and that’s your daily physical activity. Like the demands of daily life. Um, so not including structured exercise, but just kind of your daily steps, what you do for work, cleaning the house, fidgeting, all the energy that goes into those normal daily things. But then you also have you exercise activity thermogenesis.

Leah

00:06:53 – 00:07:45

And that’s your structured or your planned exercise and the energy that you burn doing those things, Um, and that’s affected by how often you’re exercising the intensity, duration and modality of the exercise. Um, and then lastly, we have the thermic effect of food. So that’s basically the amount of calories that we burn by digesting and eating food and obviously that is affected by how much we eat. So we’re eating a lot of calories, protein, fibre. We’re going to be burning more energy from the thermic effect of food, as opposed to if we’re in a very low amount of calories. So that that can come into play. But my understanding is when we’re talking about metabolic adaptation, that it’s really its effect on metabolism or basal metabolic rate and not these other three things. 

Aidan

00:07:45 – 00:08:22

Yeah, exactly and that’s where, like, I do lump them in a little bit together. I think it’s important to have an understanding of all of them and how all of its affected, but like it is like if you were looking at definitions, it is just metabolic rate. That is what we’re measuring. So I’m going to go through some things individually, like I’m gonna start off with, how does that diet impact our total daily energy expenditure? Because I think this is really important to understand, one of the best examples you touched on was the thermic effect of food. It’s so easy to understand why Calories in versus calories out is a moving target, as in your calorie expenditure changes based on what you eat. The easiest way to understand that 

Aidan

00:08:22 – 00:09:01

as one starting point, is a thermic effect of food. If you were previously eating 3000 calories and you dropped down to 2000 calories, your thermic effect of food will reduce because you were eating less food. you’re going to burn less calories through the process of eating, digesting and absorbing food, because there is less food for that to happen. So that’s one standpoint. That’s food for thought, because it’s like your maintenance calories literally change based on how much you’re eating, how far you are from maintenance calories. So it is very interesting when it’s like, hey, we predict a 500 calorie surplus. But the moment you add calories energy expenditure increases as well, like it changes these things. That’s one standpoint. The next one is based on metabolic rate. 

Aidan

00:09:02 – 00:09:39

When you go into a calorie deficit and say you were in one for a long period of time or your on particularly low calories your body, call it survival mode, call it whatever, I don’t really care. Call it Battery saver mode. Like your body starts to down regulate certain processes to conserve energy because think of it as like a physiological adaptation. I hate using these examples, but it’s kind of like your body doesn’t know when it’s going to have more access to food and stuff like that. One great example of this is when your heart rate slows down if you’re in a calorie deficit for a long period of time, or you get particularly lean that burns less calories. It’s not a lot less calories, but it burns less calories and that doesn’t fall into any other category that falls into the metabolic rate. 

Aidan

00:09:39 – 00:10:23

This is a classic example, but females losing their period. Basically, stopping fertility is no longer a priority if the body doesn’t have enough calories to look after itself. So it’s not going to spend calories on fertility. That’s just one of many examples of how a metabolic rate can drop over time in a calorie deficit. And obviously, as you’re going to higher calories, these things reverse because there’s now an abundance of calories.

The next one that I’ve always found so fascinating is neat. So as you said, it’s all incidental activity. The classic example that people give of this is that people fidget less when they’re on lower calories. They fidget more when they’re on higher calories, and this is a very individual thing. Some people fidget way more when they get higher calories, and it’s pretty individual there and the other thing 

Aidan

00:10:23 – 00:11:01

even just thinking it through. But like classic examples where it’s like when you’re on low calories or have been dieting for ages you might be more tempted to just lay on the couch rather than get up and mow the lawn or something. All these little things change, and if you follow a lot of people on Instagram who are bodybuilders, who prepped for shows. If they do a lot of videos, just watch them. They are less active in their videos. They move less. They talk slow, they blink slower. It’s crazy. It’s an actual phenomenon and actually significantly affects their calorie expenditure because it’s all movement. And then the last one is exercise activity thermogenesis, I suppose. The other thing I should touch on is the BMR before just talking about calories. It’s like 

Aidan

00:11:01 – 00:11:36

if you lose weight, like if you actually are losing weight because you’re in a deficit, your base metabolic rate drops. That is what the formula is measuring. And stuff like that, Um, fat burns like roughly four calories per kilo. Muscle burns roughly 12 calories per kilo. If you’re losing muscle and fat, this is going to decrease regardless. Same thing for exercise activity thermogenesis. If you do a certain exercise at 100 kg body weight, and then you do the exact same exercise at 90 kg body weight. You’re probably burning less calories in the second scenario, unless you’re doing more work, which obviously you can do if you get fitter and all those kinds of things. 

Aidan

00:11:37 – 00:11:45

But our diet does affect our energy expenditure. So even though a lot of those factors are outside of metabolic adaptation, they are worthwhile understanding for the sake of this discussion. 

Leah

00:11:46 – 00:12:18

Yeah, I think like metabolic adaptation, it definitely has a lot of practical or clinical relevance. Um, from one standpoint, I think it is definitely a good idea to acknowledge that it exists and it occurs. Um, so if we are in a calorie surplus, obviously there is an increased energy expenditure and vice versa if you’re in a calorie deficit, so having that understanding can be super useful. I just think some people can take that a bit too far in its significance. So it’s likely not the reason why a calorie deficit 

Leah

00:12:18 – 00:12:20

is no longer working. 

Leah

00:12:20 – 00:12:55

There’s so many things like you’ve touched on that are at play when you’re in a calorie deficit and certain things that happened even just changes in your activity levels. There’s so many reasons, Um, why that’s no longer a calorie deficit or you’re no longer losing weight. And I guess when we’re talking about this, always think about the flip side. So it’s saying, with the calorie surplus, it’s not usually the whole reason why a calorie surplus is no longer a calorie surplus. But I like to think of it more in the deficit side of things because that’s when it comes up the most. Um, so if you’re in a 500 calorie deficit for 12 weeks, so not super long period of time, 

Leah

00:12:55 – 00:13:37

you are losing weight, and then you stopped losing weight. Metabolic adaptation would not be the reason why that completely stopped. It wouldn’t account for the whole 500 calories. Um, but we’re also not completely sure exactly how much it does account for or how much it does occur. And it’s probably different for different people. Different circumstances. Um, one interesting study that I will mention, um, it came out in 2020 and it’s titled Metabolic Adaptation is not a barrier to weight loss. Um, and that study concluded that at the two year follow up post, um, the two year follow up mark post weight loss that metabolic adaptation was not present. 

Leah

00:13:38 – 00:14:02

So with this study, I mean, two years is a long time. So if we’re thinking, you know, these people have gone through a weight loss phase and then there’s been a maintenance or above calories for two years, we would expect metabolic metabolic adaptation to no longer be relevant there. Um, so I think it’s a bold claim. I just think the title is a bold claim for the study that it actually is. 

Aidan

00:14:02 – 00:14:30

Yeah, and I’ve thought about the title. So, like, a lot of people have sent this to me because, like, if you Google Metabolic adaptation, I think my article comes up first or second, and a lot of people have seen this study and then being like metabolic adaptation doesn’t matter. And they sent it to me because you write about metabolic adaptation. You think it prevents weight loss and, like, no, it actually lines up with everything we think about metabolic adaptation, like, what did you just say before about like you said, metabolic adaptation is not going to stop you from losing weight. If you’re in a 500 calorie deficit, 

Aidan

00:14:31 – 00:15:08

maybe it’s gonna erase some of that deficit. But all the other factors are going to play a role in terms of energy expenditure decreasing for other reasons and the fact that maybe you get hungrier. Maybe you change your habits. Maybe there’s a lot of other explanations that are far more likely. Um, but then exactly what I said. Like your energy expenditure, it will go the other direction when you’re eating more calories. Two years is a long time, like we expect that to happen. The other thing in the study that is the real point that a lot of people point out, is that they’re like It’s not a major barrier to weight loss. In the abstract they mentioned that they measured metabolic adaptation directly post diet. 

Aidan

00:15:09 – 00:15:50

When you read the study, they measured metabolic adaptation four weeks post diet. They’ve been at maintenance calories for four weeks, and we know from some research Jackson Pos, for example, to the diet break study where he did diet breaks for one week every four week period. They do one week diet break, three more weeks on diet, starting so on and so forth for 15 weeks. That wasn’t enough to offset metabolic adaptation. There was no observed change there. The Matador study, which did two weeks on two weeks off two weeks on two weeks off, looked like an offset metabolic adaptation. But we can’t really tell because there’s a free living study and they were just eating in the real world like it’s hard to tell them that kind of story. Maybe that is strict on the diet, really like it’s hard to say, but 

Aidan

00:15:51 – 00:16:18

I’d be very confident. One month, four weeks. That makes sense, calories are going to reverse a fair chunk of metabolic adaptation. The difference that they measured was a 50 calorie difference in energy expenditure or actually in basal metabolic rate. So it’s a 50 calorie reduction in basal metabolic rate. As I said, there’s other factors, like neat is reduced and stuff like that, like that’s beyond that. That could add on to the 50 calories as well. It could be even higher than that. You talked about individual variation. 

Leah

00:16:18 – 00:16:51

There were some people who there was no difference in metabolic adaptation that stage. There are some people who had over 100 calories different, but that’s after four weeks. I would make the assumption that there is more than a 200 calorie difference at some stage. Like if they measured it after a short washout period of like a couple of days at maintenance calories, I’d assume that there was a larger difference, that it’s safe to say that. But, like, let’s call it 200 calories. That still comes back to the same question that we’re just talking about being like It’s not going to offset a 500 calorie deficit like that. That’s not the reason why people stopped losing weight. Um, it’s just to be aware of that. 

Leah

00:16:52 – 00:17:00

Four weeks probably offsets quite a bit of this, and that study could look a little bit misleading because they measured at four weeks later, not directly post diet. It would have 

Leah

00:17:00 – 00:17:38

been really interesting if they did measure that during the diet and directly post diet. So I completely agree that it’s a little bit misleading, particularly with the title, because we just wouldn’t expect that to be a huge difference in metabolism. After four weeks at maintenance let alone in two years. Um, we definitely expect things to kind of return to normal by that time. Um, I think practically like, if we are seeing this metabolic adaptation, which I like, you said like you would see, um, some after you know, 12 or so weeks of dieting, and it probably is not the most significant factor in cutting a calorie deficit. Um, but it’s probably a factor. 

Leah

00:17:38 – 00:17:56

So I think the idea of diet breaks when we’re thinking about clinical relevance. Um, you know, I love utilising diet breaks with my clients. Diet breaks have been shown to reverse some of that metabolic adaptation I personally use to like a diet break of two weeks. How long do you tend to do?

Aidan

00:17:56 – 00:18:14

I do 2 to 4 weeks, but two is more common. Four is more if it’s like, hey, let’s take a legitimate just gap for maintenance calories. We want to do something longer. Um, that, too, is my standard, like I like eight weeks on two weeks off. But sometimes I’ll let people run for 12 weeks and then put it in then.

Leah

00:18:14 – 00:18:34

And outside of metabolic adaptation. There’s also other benefits of diet breaks, which we have talked about so psychologically. It’s good to have a break from dieting. Um, so you know, if you’re taking a two week break every 8 to 12 weeks doing that weight loss in chunks psychologically, I think that’s a lot easier. And then there’s the impact on hunger. 

Aidan

00:18:35 – 00:19:14

Yeah, And like even with the metabolic adaptation, I’m always scared now saying, oh, that diet breaks are off setting metabolic adaptation because, like Jackson Pios, he has concluded very strongly that diet breaks don’t offset metabolic adaptation. And like he’s smarter than me. Like he said, his ATAR was like a 99 8. I’m like Jesus, there’s been times I have thought stuff. And then he said the opposite of what I thought, and then he turned out to be right and like goddamn okay. But like my thought process for metabolic adaptation is, it’s like I’m sure we can all agree that if metabolic adaptation is a real phenomenon which has been measured like we can agree that it exists 

Aidan

00:19:15 – 00:19:52

We also know that going to higher calories offsets it. This is also why reverse dieting works and stuff like that, like it just slowly reverses the metabolic adaptation. We know that at some point, higher calories offsets it. The question is, how long does it take? To show that four weeks later, like metabolic adaptation, is pretty much non-existent, and obviously one year later it did not exist, and two years later it did not exist. We know there is a time frame. Jackson’s study showed that one week later it didn’t make any difference. Maybe, like maybe it takes longer. Maybe it will take two weeks. We just don’t have the evidence to show the two weeks because, as I said, all these other studies aren’t really that tightly controlled. They’re not athletes. That’s like a whole bunch of things to factor in. 

Leah

00:19:53 – 00:19:56

I think two weeks would reverse some of it. That’s my practical interpretation. 

Leah

00:19:57 – 00:19:59

Enough of it, Likely, I think so. 

Aidan

00:19:59 – 00:20:04

I think so. But I’m always cautious saying that because we do have that study that shows that it didn’t when it was only one week after a week.

Leah

00:20:04 – 00:20:35

I’m sure it depends on the size of the calorie deficit in the person and so many other factors. But if you’re putting people on diet breaks for a month at a time, quite consistently, that’s gonna be pretty slow progress and considering, like, which we’re saying that metabolic adaptation is likely not the main factor why someone is struggling to lose weight, then you know, maybe that’s not our main focus. Maybe they’re struggling to lose weight because they’re having extra snacks because they’re really hungry. You know, the diet break at least offsets hunger. 

Aidan

00:20:35 – 00:20:56

Yeah, let’s actually talk through that a little bit more like, um, Jackson’s study. That was the thing that he found, like there is this chart that I show almost all my clients. Now, there’s a chart from the study that basically showed that if you diet and you actually stick to the calorie deficit, you actually are losing weight almost every week. Um, for 12 weeks, hunger and desire to eat dramatically increases. 

Aidan

00:20:57 – 00:21:26

I think everyone needs to know that and I obviously like this individual variation, but I think that’s true because, like I have a lot of clients who like four weeks in the same stuff to me like I don’t get hungry anymore. And like I don’t crave sugar anymore. And like little, they’re saying things like that as if that’s what they expect to be happening, as in, it’s almost like they’re telling themselves that. But we have the data showing that in 12 weeks the opposite is happening like people probably are dramatically up. Regulating their cravings and stuff like that for food and everything like that doesn’t mean everybody will, but it seems to be that’s the average. 

Aidan

00:21:27 – 00:21:47

And his study showed that the group that did 15 weeks of dieting but they had those three diet breaks spread throughout. So they did the same total time in the calorie deficit, their hunger and desire to barely increased over the entire study over the entire 15 weeks. And it’s like, theoretically, that could make dieting dramatically easier for a lot of people. 

Leah

00:21:47 – 00:22:07

Yeah, so even if let’s say a metabolic adaptation really doesn’t really, it doesn’t move the needle in terms of a calorie deficit. We at least know diet breaks are useful for other things and, you know, potentially having two week diet breaks periodically. Maybe it does also help with metabolic adaptation as well. Um, so I do them.

Aidan

00:22:08 – 00:22:36

Yeah, 100%. And I suppose the last thing just popped into my mind. But it’s kind of like metabolic adaptation. What if you came from a calorie surplus? What if you came from a large calorie surplus that, like, say, like, I have some of my clients who do eight months long, slow bulks but like they are in a calorie surplus for, like, eight months. Maybe. Maybe they do a mini cut. Maybe they don’t. That’s eight months in a calorie surplus. Very far adapted in the other direction. And then at the end of their cutting phase, the difference in metabolic adaptation is probably larger than any of these studies make out as well. 

Leah

00:22:36 – 00:22:59

Yeah, And I think when we’re talking about metabolic adaptation from the perspective of a calorie surplus, like usually a calorie surplus is a lot smaller than the calorie deficit you’d use to lose weight. So I suppose we’re thinking, you know, the metabolism is up regulated when you’re in a calorie surplus. I don’t know. I always think about maybe it does have a bigger effect there than in a calorie deficit, even at least with some people. 

Aidan

00:22:59 – 00:23:03

And I’m also thinking about durations as well, because you’re often in a surplus for such a long time too.

Leah

00:23:03 – 00:23:21

Totally. This has been Episode 13 of the ideal Nutrition podcast. We hope you’ve enjoyed listening so far, but we do always appreciate feedback. So let us know what you’ve been thinking. Um, other than that, we hope you enjoyed this podcast and we’ll be back next week