Aidan:

Hello and welcome to the Ideal Nutrition Podcast. My name is Aidan Muir and I’m here with my co-host, Leah Higl and this is episode 192 where we’re gonna be talking about how much does metabolic adaptation matter. We have spoken about this topic before but this is probably gonna be the most in-depth podcast or piece of content that I have personally seen on how much does this matter? Because you’ll see out there a lot of people making it seem like metabolic adaptation is like huge and like something that’s super important.

You see people talking about like, it doesn’t really matter much at all. I probably fall more into that camp about being like, this is a real thing, but it doesn’t matter that much at all. But it still leaves a few questions out there about being like, okay, well, what does the research actually show in terms of like, what numbers are we seeing in the research? What are we seeing in practice and stuff like that? And then also, how does it change for different people in terms of like, what if we look at averages in research? But is there somebody with like a massive difference? Is there somebody who have no difference at all.

And one of the biggest questions that I’ve had for a long time that I’ve answered a bit more with my own reading over the last few years is like, how much does this matter for people with like massive weight losses and bariatric surgery and stuff like that? What type of numbers are we seeing during the weight loss, not long after the weight loss and then years later? So we’ll cover a bunch of stuff in this.

Leah:

Yeah. So two extra more general points I would like to add in regards to metabolic adaptation is firstly, we call it metabolic adaptation rather than damage because it does go in both directions. So when you have an increase in calorie intake, the opposite happens in that your energy output, your metabolic rate increases. So it is this, it is something that goes both ways, not just when you’re in a deficit, you have this metabolic adaptation downwards. And I think that is a fact that is often left out of the conversation online, but it’s very good to know.

And then the second one is technically metabolic adaptation refers to specifically your metabolic rate, but some definitions can include things like incidental movement as well. However, we will focus on research looking more so at your metabolic rate and then we will broaden the discussion after that.

Aidan:

Yeah. And on that strict definition, how it’s like strictly defined is the decrease in energy or resting metabolic rate that is more than would be predicted by a formula solely looking at the amount of weight that was lost. So that’s how they kind of like define it. Cool, so talking about research. So a large, super broad look at the research on the topic, including heaps of studies, you can find this in the show notes as well, but including heaps of studies found average reductions of around 30 to 120 calories due to metabolic adaptation in the groups that they looked at.

That’s pretty vague, a bit intentionally vague there because it’s just like this was just like this massive sample size of research looking at studies of all different durations, all different weight losses, all different so on and so forth. So it’s cool to know that it’s like, okay, if we’re looking at all these things, it seems to be a small difference like 30 to 120. But let’s go a bit more specific. Larger weight losses led to more metabolic adaptation.

Looking at people averaging 58 kilos of weight loss, they found a 200 to 400 calorie reduction as the average. That’s the thing that stands out to me in terms of like, clearly larger, more prolonged deficits have more of an impact. 58 kilos is a big weight loss. To see 200 to 400, it’s like, okay, that starts to get towards the more relevant end of the spectrum. Like this stuff is starting to matter, but that’s a huge weight loss. And that’s, I would wager smaller in terms of metabolic adaptation than what most people would have predicted. Noting it’s averages, some will be larger, some will be smaller, but I think it’s interesting just to put those numbers out there, because that’s what the data does show.

Leah:

Talking a little bit about the issue with simply looking at the practical outcomes in regards to weight loss and metabolic adaptation, we have tons of experience working with people and have seen a huge variety of cases. But in these cases, we never know exactly how many calories people are actually consuming in reality. Like we can make a plan, we can assess the outcomes, we can track the weight trajectory, all that jazz, but we aren’t physically there all the time to ensure that is exactly what that person is doing. We just don’t have that control.

So this means that if somebody has numbers that are wildly different in regards to weight loss outcomes than expected, they are number one, they are doing exactly what they have said they are doing. They’re following the plan that they’ve set out and are genuinely actually a big outlier in this way. And then secondary to that, we have cases where people are not doing exactly what they have said, whether that is conscious or not.

We know underreporting is very common statistically. But I point to this because it would be silly to make too strong of a conclusion based on just our own experience working with people if it was counter to the data where all variables were actually controlled.

Aidan:

Yeah. And that’s probably the, I’m the most why I’ve been curious about like, what, what did large weight losses look like? Like if I have a lot of people I’ve seen who’ve had large weight losses or bariatric surgery and they’re reporting quite low calorie intakes, I’m like, Oh, that’s a bit of a gap in the research. It’s actually hard for us to like, no, for sure. Like the gaps have been filled to like, we are seeing the averages.

From a practical perspective, there is one more thing that we have in addition to just like working with people, at Ideal Nutrition or Ideal DEXA clinic, we actually do measure resting metabolic rates. Like we have the option of testing this. and this does allow us to see some pretty interesting data. It is normally very good, but there is one thing that say that doesn’t make it perfect. The first thing is let’s say they’re not a client of Ideal Nutrition. They just come in and get an RMR test.

We don’t know what they’re doing leading up to the test. Even if they are, it’s like the same problem. It’s like, don’t know exactly, like we’re not there. We don’t know every single thing. So we don’t know everything that they’re doing leading up to the test. They’ll probably give us a summary, but like, once again, we’re not there. What if they were in a massive deficit before the test? What if they’re in a massive surplus? Like that’s going to change it because of quite literally metabolic adaptation.

Two, the test can be skewed by variables such as stress and stuff like that. We have people in like a relaxed environment and it should be chill and should give us a very accurate reading. But the machine’s very good in that like it’s quite literally just measuring energy expenditure. Like it’s very clearly just measuring energy expenditure while they’re resting. So that’s how we get the resting metabolic right.

But what if there’s something that changes it? Like we know for example, people have caffeine before the test, like that will increase it a little bit. There’s a few things like that that can change it. And once again, we can tell people like arrive faster, don’t have caffeine, but like there’s always a chance. So like we do have that data, but even with that data, I’m like, oh, if we see a big outlier case, is it an outlier case or was there something weird that went on before the scan as well?

Leah:

I think when I had my scan done, because we were all testing it when we first got the machine, mine came out as being way higher than I would expect. But then I looked back and I was like, oh, having that clip on my nose actually made me incredibly anxious. And the entire situation with everything sitting on my piercings was like, I was anxious. And I’m like, that is literally why mine was elevated.

Aidan:

Yeah. And like that example is something that I literally think about being like, like the fact that even just in testing, like we saw something that pop up, it should be so rare because we have people like laying down and like chilled out, but like it’s still a possibility as well.

Leah:

I’m just particularly anxious person set me off. But practical interpretation of all of this. So I would say that for a 12 week moderate deficit, we’d expect around a 50 to 150 calorie decrease in regards to metabolic rate just due to metabolic adaptation. So it’s not a super high amount, but it’s also not incredibly insignificant. And that’s not intended to be perfect. It’s just a highlight that it’s a small change that is relevant, but often not large. So if we’re talking about weight loss plateaus, it could be a factor, but it’s not usually the entire reason why someone has stopped losing weight.

The other part is duration. So in terms of how long metabolic adaptation is actually relevant for post a deficit phase, research typically finds that if you try to measure it after four weeks at maintenance, it is usually no longer there. So it’s no longer relevant. There’s no longer a drop. And the metabolic rate has increased again, but longer and more severe deficits would take longer to recover from. The body does seem to care more about what you have done recently in regards to its metabolic rate rather than the stuff you did a while ago. And I think that is just driving the point home.

Aidan:

Now we’re going to add in incidental movement into this because although the strict definition, that’s really what we’re looking at. The broader definition, including incidental movement to a degree, you could consider this more relevant because it is more of a broad change in energy expenditure in relation to being in a deficit.

This is a separate one, but like the thermic effect of food is also in here being like if you reduce your calorie intake, calorie expenditure due to the thermic effect of food decreases. Incidental movement typically does decrease. We have spoken about this a fair bit, but like this could look at, say somebody’s not tracking their daily steps, typically somebody in a deficit for a long period of time, their daily steps will just naturally decrease. There’s less of an urge to do any task involving physical activity that’s not kind of mandatory. And there is also people literally like, slowing down their movements.

Like the classic example I always talk about is blinking slower and stuff like that. Like it’s a lot of things that are subconscious, a bit outside of our control. So when we do add those in, there usually is a larger reduction as well, which once again, when we come back to that kind of plateau thing, it’s like maybe it’s a portion due to the metabolic adaptation. Maybe it’s also a portion due to the incidental movement amongst other things.

Looking at research is harder on this one though, just because it is very individual, it’s actually way more individual than metabolic adaptation and just hit some people harder than others. you can also, it’s semantics about whether like intentionally doing more daily steps is incidental if you’re like, I’m going for a 30 minute walk. Like that’s no longer incidental, you’re just exercising to a degree at that stage. But you can also just offset it quite easily just by like, this is why bodybuilders have step targets and stuff like that during their prep.

So it’s worth knowing that this has a larger fluctuation in most cases than metabolic adaptation, adds to the picture, but I’m not actually a stage where I want to put numbers on it, partly just because it’s a lot, you can do a lot of things to intentionally offset it and things do change a fair bit.

Leah:

So adding all this up, metabolic adaptation by itself typically isn’t a huge deal, but the bigger the loss, the more significant this drop in metabolic rate can actually be. But even in those cases, on average, the numbers are not super large.

Adding the incidental movement aspect into it makes it a larger thing, as Aidan was saying. So often working towards keeping your activity, your incidental movement up, yeah, semantics around whether that becomes structured at that point, but you can do things to offset that component.

We also know that appetite and desire to eat often increase the longer a deficit goes on for. This isn’t super relevant for today’s podcast, but we’d like to highlight it just because when, again, plateaus in the context of weight loss plateaus, this is something to think about. And when there is a plateau, it’s almost never just going to be one thing. And it’s definitely never going to be just metabolic adaptation. There are going to be several likely variables that go into why someone has plateaued in their weight loss. And yes, it can be useful to think about metabolic adaptation as part of overcoming that, although it’s a small contributing factor.

Aidan:

This has been episode 192 of the ideal nutrition podcast. As always, if you haven’t already, please leave a rating review that would be massively appreciated.