Bei jungen asiatischen Männern konnte durch vierwöchiges Fasten am zweiten Tag das Körperfett erfolgreich um 1,6 kg reduziert werden, es kam aber auch zu einem Muskelverlust von 0,8 kg, den eine kleine Proteinergänzung nicht verhindern konnte

‘Future studies should explore the effectiveness of protein or leucine supplementation, throughout the feeding and fasting days, in terms of preserving muscle during weight loss’.

Fingers crossed I guess.  Losing weight without losing muscle as well is always the challenge.

There isn’t any mention of weightlifting. You need to train your muscles ever so slightly if you want to avoid losing them.

Nothing surprising there. Any kind of sudden calorie deficit diet causes the body to take the energy where it is most easily accessible – the protein in the muscles. Burning fat is much harder and that only kicks in after some time.

This is why yo-yo dieting is such a bad idea, especially for women who start out with less muscle mass. Diet, lose muscle; fall off the diet, add more fat. Diet, lose more muscle; fall off the diet again, add more fat. It’s a vicious cycle that makes the situation worse and worse.

Fasting may or may not have other benefits but it’s not really a great way to lose weight. A great way to lose weight is a lifestyle change, eliminating excessive carbs and sugars, and eating vegetables and lean proteins.

Exercise is for becoming stronger and healthier and is optional for weight loss.