Boyfriend eats badly?

My boyfriend eats really badly and I try to tell him to stop eating fast food, and things like ravioli (in a can). He is pretty skinny... and he eats a lot of chips and soda so he's lucky. I just want to help him eat better but I cant always be there with him until we eventually move in together. His parents all buy crap, do you think there is another way to help him out? He cares about him eating badly but I guess not enough to tell his parents to buy better food.