Can Weight Loss 'Damage' Your Metabolism?

There's much discussion on metabolic damage: the idea that weight loss could slow down your metabolism - forever. Should you be worried about it?

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There’s plenty of anecdotal evidence going around in the corners of the Internet forums (think: Reddit and Quora), claiming that dieting can permanently wreck your metabolism ?‍?️️

And it’s not just anecdotal evidence.

A widely-publicized 2016 study that looked at former contestants of US reality TV show, ‘The Biggest Loser’, also found that the participants had to eat up to 500 calories fewer than expected (based on their body composition) daily for weight maintenance, even several years after their initial weight loss.

So. Could ‘metabolic damage’ be the reason why nearly 90% of people who lose a lot of weight eventually regain just about all of it? Also: what would this mean for those trying to shed excess weight (like you, perhaps)? Let’s explore.

Yes, dieting ‘slows down’ your metabolism

First things first. Be aware that, yes, dieting does slow down your metabolism.

Suppose you're truly eating in a calorie deficit.

In that case, you will start losing weight – and that, in turn, brings about several adaptations in your body meant to reduce your daily energy expenditure.

Before you get all shocked, note that a few of these adaptations are entirely normal and expected.

For instance: a smaller body requires fewer calories to sustain itself.

Thus, it'd make sense that your body would require fewer calories to stay at maintenance than at the beginning of your diet (when you had a 'bigger' body, for lack of better phrasing).

Another expected – and well-documented – diet-induced adaptation is a slowdown in your non-exercise energy expenditure (NEAT).

A quick refresher for those who need it: NEAT refers to the energy your body burns for everything you do that's unrelated to sleeping, eating or sports-like activities. It could refer to fidgeting, typing, walking, and even performing yard work.

Now, back to the topic on hand. Why is a reduction in NEAT expected?

Well, that’s simple. If you’ve ever dieted before, you’d know just how mentally (and physically) sapping the entire experience can be.

And it's not just your mind playing tricks on you.

Scientists believe that the body enters something like an 'energy-conserving' mood in a calorie deficit –  explaining why you'd only want to lie around, binge-watching The Office re-runs for the 1,000,000th time when you're in a calorie deficit.

These 2 adaptations are typical.

But another adaptation's raised many eyebrows (plus, it also happens to be the one cited as 'proof' that metabolic damage is real).

What is adaptive thermogenesis? What is metabolic damage?

What is this controversial adaptation? If you’re someone who reads article headings, you’d know. It’s none other than adaptive thermogenesis (AT).

Because you must be wondering: AT refers to a greater-than-predicted drop in metabolic rate after weight loss – beyond what should be expected based on body composition (i.e., lean mass and fat mass).

Here’s an example to illustrate.

Let's say someone loses weight, and the expected drop in metabolic rate was 200 calories. In actuality, though, the reduction in metabolism post-diet ends up being 300 calories instead. That difference? The additional 100 calories decline is adaptive thermogenesis.

You might be wondering … wait. What about ‘metabolic damage’? What’s the difference between adaptive thermogenesis and metabolic damage?

As its name suggests, metabolic damage is simply the idea that weight loss destroys your metabolism. Spoiler: it doesn't.

This is in direct contrast to adaptive thermogenesis, which has been observed in numerous studies.

Confused? I thought you might be. Because if adaptive thermogenesis is real, isn't it solid proof that metabolic damage is real, as well?

But dieting doesn’t damage your metabolism

No. And here’s why: it appears that a large part of the decrease in calorie expenditure through adaptive thermogenesis can be traced back to the reduction in NEAT levels – instead of in the resting metabolic rate.

More specifically, it appears that a drop in NEAT levels can account for as much as 85% to 90% of the decline in energy expenditure commonly attributed to adaptive thermogenesis.

Going back to our previous example: let’s say that your post-diet drop in metabolic rate comes to 300 calories.

Your NEAT would explain 270 calories of the 300 calories. That means you can only pin the remaining 30 calories on your ‘slowed-down’ resting metabolism rate. Read that again. 30 calories! For reference, a small apple contains 78 calories!

So, one thing’s clear. Dieting doesn’t damage your metabolism! Or even dramatically slow down your metabolism at all.

Of course, there's no denying that you'd experience – at least to some degree – adaptive thermogenesis. But even then, the non-NEAT portion will be so small that it wouldn't influence your ability to keep the weight off.

What does this all mean for you?

Alright. Dieting doesn’t damage your metabolism; that’s fantastic news! Only … why can’t people keep the weight off, then?

Well, it's because they're unable to stick to the methods that they initially used to get all the weight off in the first place.

Think unsustainable, restrictive diets like the ketogenic diet, the Paleo diet, or even Intermittent Fasting.

There's a lesson to be learned here. If you're currently trying to lose weight, you've got to make sure you’re going about it in a sustainable manner – one that you can see yourself doing for life.

Otherwise, it's pretty much pointless. Because chances are, you're going to end up in the 90% statistic and put all that weight back on in just a few years.

What about those of you who’ve already lost all that weight?

Luckily for you, a 2018 paper outlines the various strategies employed by individuals who've managed to maintain their weight loss results for the long term.

In other words: these people have managed to counteract the metabolic compensation (i.e., adaptive thermogenesis) following weight loss.

For your benefit, here are a few tips summarized from the paper:

In case you were wondering, no, you shouldn’t be in a long-term calorie deficit.

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Then check out GymStreak. This AI-powered workout app plans all your workout routines for you according to your unique fitness goal(s) – and even helps you learn how to master a specific lift through its virtual reality 3D projections. All you need to do is show up.


Clamp, L. D., Hume, D. J., Lambert, E. V., & Kroff, J. (2018). Successful and unsuccessful weight-loss maintainers: Strategies to counteract metabolic compensation following weight loss. Journal of Nutritional Science, 7, e20.

Fothergill, E., Guo, J., Howard, L., Kerns, J. C., Knuth, N. D., Brychta, R., Chen, K. Y., Skarulis, M. C., Walter, M., Walter, P. J., & Hall, K. D. (2016). Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity (Silver Spring, Md.), 24(8), 1612–1619.

Rosenbaum, M., & Leibel, R. L. (2010). Adaptive thermogenesis in humans. International Journal of Obesity (2005), 34 Suppl 1, S47-55.

Rosenbaum, M., & Leibel, R. L. (2016). Models of energy homeostasis in response to maintenance of reduced body weight. Obesity (Silver Spring, Md.), 24(8), 1620–1629.

Trexler, E. T., Smith-Ryan, A. E., & Norton, L. E. (2014). Metabolic adaptation to weight loss: Implications for the athlete. Journal of the International Society of Sports Nutrition, 11, 7.

Wang, X., Lyles, M. F., You, T., Berry, M. J., Rejeski, J., & Nicklas, B. J. (2008). Weight Regain is Related to Decreases in Physical Activity During Weight Loss. Medicine and Science in Sports and Exercise, 40(10), 1781–1788.