I've noticed it as well. It is somewhat interesting to think about. I imagine many of them are at some level in psychological pain and rely on booze and other vices more than the normal populace. Also, they're gangsters--the fast life, fast money, women, that is what the lifestyle is about for many of them. Also they largely come from working class or poor backgrounds, where health habits tend to be worse. Finally they are Italian so they love to eat.