The Vitamin #92: Does Adaptive Thermogenesis Make Weight Loss Maintenance Impossible?

06 Oct 2022 | by Aadam

Hey there,

It’s time for another instalment of the Vitamin––the weekly fitness newsletter that helps you be healthier, stronger, and leaner while navigating fitness bullshit.

Chances are if you’re reading this, you’ve heard of adaptive thermogenesis. Maybe not that term exactly, but how about metabolic adaptation or the misrepresented and bastardised version some people call metabolic damage?

Regardless of the name, they all refer to the same idea: The greater than predicted drop in metabolic rate after weight loss, beyond what should be expected based on fat and fat-free mass changes.

For example, if someone loses weight and the expected drop in metabolic rate was 100 calories, the actual drop in metabolic rate might end up being 150 calories. Those additional 50 calories (beyond what was expected) is adaptive thermogenesis.

Some people claim that adaptive thermogenesis is what causes people gain the weight back at the end a diet due to a massive suppression in their metabolic rate. Consequently, these people need to eat at a caloric intake way below what they can maintain, which eventually causes them to quit and gain back the lost weight.

So, is adaptive thermogenesis the root cause of all weight maintenance failure?

Let’s talk about it.

First, let’s quickly recap the basics: To lose fat, you need to eat fewer calories than you burn; there’s no way around the first law of thermodynamics.

But that doesn’t mean it’s a linear process.

The body has mechanisms in place to stop you from losing weight, which is why you might start off reducing your energy intake by 500 kcals and lose weight just fine initially. At some point, though, you’ll find progress slows down, and further adjustments need to be made as the different components of the metabolism adapt.

The mechanisms that try to prevent you from losing weight are collectively referred to as metabolic adaptation (or adaptive thermogenesis) and is a totally normal occurrence during any weight loss diet.

But what about after the diet ends? Could adaptive thermogenesis affect your metabolism to such a degree that it makes weight maintenance impossible?

Some studies have suggested adaptive thermogenesis could be a barrier to weight loss maintenance, with some even suggesting it hangs around after a diet ends. 1 2 3

However, not all research agrees. Other studies have found adaptive thermogenesis is diminished or disappears entirely after a period of weight maintenance. 4 5

A new study adds to the topic by investigating whether adaptive thermogenesis is present in a group maintaining their weight loss over an 8-month period. 6

In this study, 94 former elite athletes were randomised to one of two conditions:

  1. Intervention/weight loss group: Completed four months of active weight loss followed by an 8-month weight maintenance period with dietitian consultation throughout.
  2. Control group: Were put on a waiting list for the 12-month duration (for ethical reasons, these participants were then given the weight loss + maintenance intervention described above after the 12 months).

Measures of body composition (weight, height, fat-free mass, fat mass), and energy expenditure (resting, physical activity, and total daily expenditure) were measured at baseline, after the 4-months of weight loss, and then at follow-up 8 months later.

All testing was completed after a period of weight stability––this is super important as testing while weight is changing could confound the results.

For example, one study found when testing was done immediately after participants lost 14kg (~30lbs) metabolic adaptation was 92 kcals/day. However when researchers measured metabolic adaptation after 4 weeks of weight maintenance, this number dropped to 38 kcals/day. In other words: testing for metabolic adaptation directly after weight loss, while participants were still in a deficit, inflated the number by 2.5x the actual amount.

What did the researchers find?

  • The intervention group successfully lost weight over the first four-month period of weight loss (-4.7kg) and then maintained this weight loss over the subsequent 8-months of weight maintenance (-5.3kg).
  • The control group didn’t experience any weight loss at the 4-month (+0.3kg) or 12-month mark (+1kg).
  • Both groups were at energy balance at the 12-month time-point.
  • Predicted and measured resting energy expenditure were decreased in the intervention group at 4- and 12 months (i.e., after weight loss and weight maintenance, respectively).

What to make of this?

The findings of this study suggest adaptive thermogenesis is present after a moderate amount of weight loss (~5% of baseline), and this effect persisted after a subsequent 8-month weight maintenance period.

So these findings are consistent with some previous research that reported adaptive thermogenesis persists after weight loss but disagrees with other studies that haven’t observed an effect of dieting on adaptive thermogenesis.

I know. The inconsistency between studies can be frustrating. But the differences in study results can likely be attributed to individual study design.

For example, Nunes et al. conducted a systematic review examining whether adaptive thermogenesis occurs after weight loss in adults before and/or after a weight maintenance period. The researchers noted the same inconsistencies in studies but found studies that used higher-quality methodology and design were also the studies where adaptive thermogenesis was small or non-significant. 7

But let’s return to the question asked earlier: Could adaptive thermogenesis affect your metabolism to such a degree that it makes weight maintenance impossible?

Probably not.

For adaptive thermogenesis to truly impact someone’s ability to maintain their weight (or even lose weight in the first place), it would need to increase by an amount that would lead to a significantly reduced total daily energy expenditure.

But that’s not what we see in the research.

In the present study, adaptive thermogenesis was about 60 kcals/day. A 2020 study found adaptive thermogenesis to be about 54 kcals/day. And two other studies––one published in 2021 and the other earlier this year––found adaptive thermogenesis to be 54 and 46 kcals/day, respectively. 8 9 10

So it’s like, do you really think those 50 or so kcals are really going to impact your progress and ability to maintain your weight or is it all the other things people do, like not paying attention to how much they eat, low levels of NEAT and physical activity, especially strength training, etc.?

Considering the above, it’s no surprise then that studies have found adaptive thermogenesis isn’t a risk factor for weight regain.

A few years back, I was having a conversation with a friend about metabolic adaptation, and he quipped, “People worry so much about metabolic adaptation but nobody talks about behavioural adaptation.”

He’s right.

The behaviours and habits you adopt are going to have a far greater impact on your ability to both make and maintain your progress than some transient adaptations that occur during weight loss (I say “transient” because the better studies on the topic seem to suggest metabolic adaptation/adaptive thermogenesis dissipates once you return to maintenance).

Here’s an example of what I mean. In the present study under review, researchers found participants slightly decreased their sedentary time and increased the amount of physical activity during the 4-month weight-loss period.

However, by the end of the study (12-month mark), the participants increased their sedentary time, and their physical activity levels dropped back to baseline. As the researchers note:

The lack of a successful WL [weight loss] and its maintenance may be mostly due to behavioral issues, such as increasing food intake and/or decreasing physical activity.

And isn’t this what we see in the real world?

Someone starts a fad diet and does all the things for a few weeks or months, then as soon as the diet ends, they go right back to their old behaviours, and gain back the weight.

Here’s the thing: People wrongly assume maintenance is this thing that happens after the diet ends. But the truth is maintenance begins on day one of your diet.

The same habits and behaviours that will help you lose weight are the same things you need to do to maintain your weight–

– Eating a majority whole food nutrient-rich diet with adequate protein

– Not restricting foods you enjoy but learning how to make these foods a part of your eating plan

– Trying to get in movement throughout the day and being as physically active as is feasible for you

– Focusing on strength training to build and maintain your muscle

This is why you need to look at how you’re currently approaching your fitness goals and ask: Is this something I can maintain for the long term? Because if it isn’t, you’ll struggle to make (and later maintain) progress.

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