It would be helpful in figuring out the necessary caloric intake of the boy if the height and current weight was known. but if we assume the boy to be 100 pounds, 5 feet tall, and very active, then he'll need to eat 2000 + calories to maintain his weight. If he wants to build muscle, like most pre-teen boys do, he'll need to eat at least 2500 and be very active. concentrating on consuming protein couldn't hurt either. i guess it's true what they say, "a growing boy needs his food".