In general how much does a moderate amount of weight lifting increase shirt size starting from no muscle mass? Not body building or anything just going from a sedentary lifestyle to a decent amount of bulk. I've been redoing my clothing collection and don't want to buy too many smalls if that will go to a medium in half a year. I'm a 35-chest, 31 sleeve right now and the smalls have a bit of extra room in them. Also, how does this apply to outerwear? I find that smalls in shirts have a bit of extra room for me, whereas outerwear fits just right. Are you always supposed to size up 1 for outerwear? Thanks!