I'm not 100% on this as I've never wanted to get bigger, but isn't the idea behind high protein intake that it builds you up after the workout? If so it's not going to do him a lot of good considering he can't do heavy workouts and so it'll just make him bigger with no definition
Also Robbie you're like 12 or 13 can't remember but that's too young to be tearing up your muscles (which is how it all works basically) as it can then damage your natural growth - like I say, I'm not into bodybuilding but back when I was in school there were actual laws against the schools letting people under 14 use big workout equipment

















