How much muscle is lost when prolonged fasting?
If one were to lose 1 kg by doing a prolonged fast, how much of this would be muscle? Just an estimate.
Ignore water weight.
Personally I like to provide answers as best I can even if the question is vague. But this is far too vague. Each persons starting situation is very unique. How long is the fast? How much lean body mass vs fat do they have? I can’t think of a simple way to give you any sort of meaningful answer.