Diet and exercise. As for what exercise, he needs to work on running, "core" strength (abs and back), and upper body strength for pushups/situps. He doesn't need to bulk up since that would actually hurt him losing weight, but if he starts running now and making a no-compromises switch to only healthy food (in reasonable amounts), he ought to hit his goal without any problem and also be in decent shape for basic training.
As for what constitutes healthy food, that means absolutely NOTHING deep fried. Not one single french fry. Cut out sugar drinks, including gatorade (but real fruit juice is ok in moderate amounts). Eat some sort of fruit or vegetable every meal, and in those meals eat some sort of lean meat no bigger than the size of the palm of his hand, then fill up on veggies, fruit, and non-processed carbs like rice.
He'll feel better and lose weight at a sustainable rate without feeling tired all the time. If he needs menu ideas, check out the phase 2 and phase 3 suggestions from south beach. Skip phase 1 and don't worry about all of the restrictions in phase 2 since he's young and ought to be exercising enough to burn off any excess carbs, but the menu ideas from that plan are very healthy and don't have "bad" foods that a lot of people habitually eat because they just don't know any better.
