It sucks. My one friend went from pulling some pretty good stuff in his high school / college years to being a chubby chaser in his 30's now. I could tell similar (and far worse) stories about other people around me.
So I decide i'm going to do a good deed.. dozens of times I talk to them about diet, offer to workout with them, offer to start them out with just one muscle group like biceps. Nothing. Nada. Its like, they can't connect that A+B = C. That they will likely be boning fat and/or homely chicks the rest of their life unless they make a change (get rich or get big two obvious ones).