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.
Thanks for the advice.
It just mimics what my husband tells him (hubby has weight trained for years.)
We're constantly pushing protein shakes and protein bars at him to eat between meals.
But it's hard to force a 17 year old to eat, LOL, and he doesn't seem too concerned about being "skinny."