I’m 18M (5ft6in) loosing around 400 grams daily since last two weeks following my daily ritual . My daily ritual is eating for only 4 hours(2pm to 6 pm) ,then I do high intensity workout for 2 mins (I run up stairs as fast as possible for 6 floors) then I play football daily from 10 pm to 11 pm . I’m in fear that I’m loosing muscle mass . I’ve lost some inches around stomach and chest . My current weight is 88 kg and is it normal to loose 400 grams every day?
The initial weight loss is usually mostly water. You might lose muscle mass if you’re in a big caloric restriction and/or if you fast more than roughly 48 hours.
To limit loss of muscle mass you should make sure you eat enough protein daily (look up how to calculate your minimum) and also make sure you do strength training regularly (a couple of times per week).