Do you “damage” your metabolism after a long period of dieting?

It has been thought that after a long period of restricting your calories, you may have a permanent adverse effect on metabolism. But what does the literature say? I read a recent systematic review (Metabolic Damage: Do Negative Metabolic Adaptations During Underfeeding Persist After Refeeding in Non-Obese Populations?) which looked into it. 

Metabolic damage refers to a weight loss-induced decrease in resting metabolic rate (the rate at which your body burns energy when it is at complete rest) that is beyond the value expected from the person’s present body composition which persists after introducing more calories and weight regain. The systematic review looked at various studies of RMR during and after weight loss due to caloric restriction (ie the Minnesota starvation experiment, in studies of chronically malnourished people, and even in case studies of bodybuilders and wrestlers). Their findings contradicted the hypotheses that RMR permanently slows down to favor fat gain when more calories are introduced and that RMR is permanently damaged by undergoing a prolonged period of caloric restriction. They found that in these studies RMR actually returned to baseline after dropping due to caloric restriction, and in some cases actually was increased when calories were increased again. Positive energy balance (increased calories) undoes the negative metabolic effects of the adaptive thermogenesis that takes place during caloric restriction and causes RMR to return to a level that  is appropriate for that person’s body composition at that time. Thus their findings showed that human metabolism is actually highly plastic and rapidly adapts to changes in energy availability and body composition.

Although you won’t find the term in any dictionary, reverse diet is a term used to describe a period after a calorically restricted eating protocol during which you slowly work to increase calories back to a maintenance level. Using this strategy, and by assessing progress weekly and tracking increases in body fat in comparison to lean muscle mass, athletes can recover their metabolisms and increase calorie intake with minimal increase in body fat.

A reverse diet may also be implemented to accelerate fat loss and avoid a fat-loss plateau when dieting. This tactic can recuperate essential metabolic hormones such as T3, testosterone, and leptin, which become down regulated during extended dieting.

The most obvious benefit is the ability to avoid the dreaded post-diet rebound. By increasing calories incrementally, a reverse diet allows your metabolism to reignite and catch up to the surplus calories. 

The psychological benefit of reverse dieting is vast. By controlling yourself and having a structured plan post-diet, it is less likely that you will experience the rapid weight gain and discomfort that often lead to depression and body dissatisfaction. The goal of the reverse diet is to increase calories with minimal weight gain. 

Take a look at the full article if you’re interested!

https://journals.ke-i.org/index.php/mra/article/view/908