Metabolic damage: a scientific review

Metabolic damage. It’s every dieter’s worst nightmare. The theory of metabolic damage states that your metabolism slows down permanently, i.e. is damaged, after prolonged periods of being in energy deficit. This decrease in energy expenditure has been used to explain the occurrence of the yo-yo effect whereby people that have dieted for a long time often quickly regain their lost fat when they stop dieting.

 

But so far no scientific publication has actually scrutinized the theory of metabolic damage, so the Bayesian research team sought to investigate whether metabolic damage actually occurred. Our findings have now been published in the Medical Research Archives.

 

Read the full paper in the Medical Research Archives (open access).

 

For a less technical and more lay friendly explanation, see Menno’s opening statement in the reverse dieting debate with Layne Norton, Eric Helms and Peter Fitschen.

 

Short summary

Human metabolism is strongly affected by an individual’s body composition, with lean body mass, in particular organ mass, having a strong positive relation with energy expenditure and fat mass having little direct effect on energy expenditure. However, fat mass stores do relate with adaptive thermogenesis, the phenomenon that your metabolism, particularly your non-exercise physical activity level, decreases along with body fat stores.

Secondly, human metabolism is significantly affected by energy intake with higher energy intakes resulting in higher energy expenditure.

When you take body composition and energy intake into account, there is no evidence of metabolic damage in the literature. This includes anorectic women, malnourished individuals, research for the Second World War on the effects of starvation, bodybuilders during contest prep and wrestlers that aggressively make weight for their competitions. Human metabolism adapts, but even in extreme cases it does not suffer permanent damage. As such, metabolic damage can be considered a myth.

 

12 Comments

  1. Jason says:

    Dr. Rudy Leibel has been working in this field since late 80’s and (at least as late as 2012) has come to conclusions of altered set point once individuals have gained weight, then reduced to lower weight. source: https://www.youtube.com/watch?v=2i_cmltmQ6A&t=5m27s

    Menno, what are your thoughts on this roughly 2.5 min clip?

    • Jason says:

      i.e The thing I’m most curious about is NOT if a 200lbs male who diets down to 150lbs, and then regains the weight back has reduced metabolism now back at the same 200lbs weight (assuming body composition has not changed). It think this has been well documented that it does not. Your paper illustrates this. But rather I’m curious about the REVERSE. That is, if a 150lb male gains weight to 200lbs and later diets back down to 150lbs is his metabolism the same in terms of RMR (when correcting for age, body composition, etc) as it was when he was initially at 150lbs.

      And maybe the bigger question is: does it matter — are these two scenarios the same or different?

      It think they are different because the question proposed is can “set point” become raised by weight loss OR weight gain?

      • These 2 scenarios are identical: see the overfeeding sections of the paper. There’s no such thing as a genetic set-point of body fat percentage that your body tries to get to.

        • C says:

          Because a short period of overfeeding doesn’t alter RMR doesn’t preclude the possibility that a long period of overfeeding, as happens for most obese people, would alter RMR more permanently. Your review didn’t look at any studies of formerly obese people. However, if the RMR isn’t permanently changed in the severe case of anorexics, i highly doubt it’s permanently changed for severely obese people either.

          Very interesting review, thanks. It supports the idea that weight training during weight loss may help prevent a rebounding of weight later.

    • The whole concept of a set-point is a myth. There’s only a natural equilibrium effect. The truth in this message is that most people that go on a weight loss diet lose fat and lean body mass and therefore end up with a lower metabolic rate than before the diet.

      • Connor says:

        1. As far as lean mass is concerned, how pronounced can the loss be compared to fat? I know many people that prefer a steep deficit on their cuts; curious to know whether loss of strength is mostly due to nutrition/being flat at the time, muscle loss or some combination of the two.

        2. Is there a link to the full literature on metabolic damage? I’m only getting the abstract, no access to the full piece. Would love to read the expanded version.

        • 1. There’s no limit in principle, but if you’re losing more than 25% LBM in practically any scenario, something’s wrong.
          2. The article is open access: you can read the full text on the journal website.

  2. Malte says:

    What do you make of the relatively new studies involving the ‘America’s Biggest Losers’ participants? There was a long article in the New York Times about it, and it seemed to be a big discovery.

    Short summary: They followed 14 contestants of the show, where extremely obese people underwent an extreme regime of grueling exercise and near-starvation for several months. That was six years ago. All of them lost huge amounts of weight (more than 100 kg in some cases) during those months. But, six years later, ALL of them with only one exception are as fat or in some cases even much fatter than before. The one person who managed to stay lean only does this by doing cardio EVERY day for several hours, and is in a constant fight against ravenous hunger.

    The reason: They compared energy expenditure in the rested state, once before the show started, then after the show ended and then now, six years later. Results: The participants had average metabolism before they started the starving/exercising and sharply lower metabolism after the show – which is totally expected because the body adjusts to starvation. But then the devastating surprise: All of them STILL had sharply lower energy expenditure now, six years later. The extreme weight loss regime seems to have inflicted permanent, severe and irreversible metabolic damage. Basically these people are condemned to be fat forever.

    But according to this post, that should not be possible…?

    Source article: https://www.nytimes.com/2016/05/02/health/biggest-loser-weight-loss.html

  3. Adnan says:

    So according to the study, basal metabolic rate is determined by body composition and not caloric intake.
    So if person A is 100kg and person B is 100kg with the same lean body mass and fat percentage, holding all variables constant, if person A is on 1250 calories daily and person B is on 2500 calories daily , the basal metabolic rate should be the same for both and that just because person A is on half the calorie amount, his metabolism would not be any slower because his body composition is the same as person B? Is this correct?

    • No, BMR is also affected by energy intake, so person B would have a higher BMR. That was one of the more novel findings of our review. However, BMR is affected only by *acute* energy intake, so it is unaffected by, say, how many calories you were consuming during your last contest prep.

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