F.B.
You didn't mention how old your son is, but I'm assuming a teenager or younger and with that much exercise, he can eat anything. What you want is a balance, make sure he gets some fruits, some veggies, some meat/protein, lots of carbs (some of which come from fruits and veggies) and fat is important too. If he's eating a balanced dinner, even having a desert of some kid every other day or so is fine. If he's hungry, snacks are fine too, just as long as he's not replacing healthy food with unhealthy, you just want to have some from every category and slightly more from the health ones than unhealthy (ie...300 calories from health food, 150 calories from un; that's just an example he needs WAY more than 450 calories a day). Also, just as a fun side, desert was created as a way to load up on calories in a small amount of food for people before the industrial revolution, so if he needs more calories, he can get them there, but make sure he's getting the most from nutritious food and stay away from the most processed and fast foods (i would rather feed my kid ice cream for dinner than mc Ds, but he only gets that once a year on Fat Tuesday).