Well, first of all. IMO the best diet is the one you don't have to pay for. Especially, when you can get past all the bald guys with plastic swords constantly slirping on themselves.
Obviously, the staples are there. High fat and protein to preserve muscle. And lower/alter carb intake except after workouts. Increase cardio.
I know that their is endless debate over the cardio issue. But if you have been around enough college athletes in your life you will see that sprints are the answer to your prayers.