Well, 15% Bodyfat is average for an American male in their early 20's, which means you're "average" in a nation of fat asses. At your age I could eat just about anything I wanted and maintain 10% BF. Once my metabolism started to slow in my late 20's it was a rude awakening and I had to start from scratch learning how to diet and eat properly on a consistent basis. It's best to learn early and keep your bodyfat under 12%.
I used to spend more time on this board actually than I do on the chat board, but that was waaayyy back in the day, like a few years ago under a different account.