Well, Josh, in your favor is the fast metabolism of youth. At your age, you can stay thin on a diet that in 20 years will make you fat. But, it sounds to me like your diet is not ideal, and at some point, it's going to catch up to you. I mean, c'mon, deep fried food is some of the worst stuff for you. And, don't count on a vegan diet necessarily keeping you slender, either. I live in a town with a lot of vegans and vegetarians, and a significant number of those people are overweight.
I don't know what else to tell you. The only thing that'll make you fat is what you choose to eat, and if you've resigned yourself to an eating out lifestyle full of fast food, the only advice one can give you is to control your portions.