After what time period will I start to lose muscle if I fast?, I am attempting a 60 hr fast and want to lose no muscle, should I do a 48 hr one or some other duration?
In addition to the comment from /u/Prokir I suggest you could do a mild workout if you’re concerned about losing muscle.
I’m quite sure without working out your body will get rid of (extra) muscle as well wether you’re taking in calories or not.