Buy him a DDR game. He'll lose weight.
Seriously though, it's not playing the games that makes them gain weight, it's what they eat.
My son is 6'1" and only weighs 140, wish we could put some weight on him. His dad has him working out on gym equipment and he seems to be gaining muscle, but he's still skinny. But he doesn't have an appetite for snacks.
Eats his meals and that's it.
I wish I was your son.
Mom.
He needs to eat more. It's good that he doesn't like snacks/candy. 6 meals per day. Start with 180 grams of protein and 300 grams of carbs per day. Weight train with No cardio. Eating combined with weight training will pack on the muscle.
WHAT is "DDR?"