>An average 30 year old who is not doing sports will not lose muscle mass by itself. >An average 50 year old will lose 1% per year or so. Sure, but the averag

>An average 30 year old who is not doing sports will not lose muscle mass by itself. >An average 50 year old will lose 1% per year or so. Sure, but the average is what it is because most people barely exercise, especially when they're older. If everyone lived a much more active life with more strenuous exercise, the average would look completely different.