I have updated the answer with a link. Vegetarianism is different in his religion, they consider eggs meat so he wouldn't eat a birthday cake. He can't eat anything at other people's houses because they're very strict with the restrictions. He's a lot more comfort eating stuff like cookies now.

I'm not saying I only serve meat in my household. I spend my own money buying him treats when I know he's coming over because he likes them. He is coming over more often FOR the food. I would feel awful if I gave him the same stuff his parents give him at home when he clearly likes normal food better. Lots of dishes he isn't allowed to eat are quite balanced and do contain vegetables. It's his family that don't know balance