How Much Fat vs. Muscle Do You Lose In Popular Diets?

Egis R.
7 min readNov 27, 2021

I’m going to inject a little realism into your world — you could lose 15 pounds of weight (~7 kg), but your body composition may be worse off.

You see, weight loss is often accompanied by a loss in lean body mass — muscle tissue and its transient contents. This loss in lean body mass has multiple negative health implications one of which being a subsequent body fat overshoot aka weight regain.

This is because less lean body mass means lower resting energy expenditure aka “slower” metabolism.

Now, for purposes of description, enjoy this view:

Minnesota Starvation Experiment

This is the Minnesota Starvation Experiment during which conscientious objectors of war went through 24 weeks of semi-starvation study — their calories were cut by about 50%.

Folks probably whined, wheedled, complained, and yet each of them had to go through the trial to lose about 25% of the original weight. They reached the limits of human leanness of 4–5% body fat.

But here is the interesting part:

The subjects were put on 8 weeks of ad libitum refeeding phase during which they regained all the fat that they have lost. But it didn’t stop there, my dear internet human​​ — they kept gaining fat until they regained lost muscle mass:

The relationship between muscle loss and fat regain

So if you want to have a successful weight loss, don’t be the individual who only cares about the number on the scale. Even more important than overall weight loss is sustainably losing fat mass while maintaining lean body mass.

This is why I have done some digging on your behalf and found the study that looked at popular diets and their ability to preserve lean body mass. Here are the diets that researchers looked at:

1. Very low calorie diet

Very low-calorie diet often includes a drastic reduction in calories. Usually to 400–800 kcal/day. Makes you drink meal…



Egis R.

I’m Egis, an online weight loss coach who has heightened BS sensors for fitness & nutrition. Only evidence-based & sustainable fat loss.