Should I be concerned about my boyfriends son's eating habits

My boyfriends son is 14 and he is really into weight lifting. My boyfriend bought him some weights and he has his own weight room. He works out a lot, which isn't a problem, but he doesn't really have the best eating habits. He doesn't eat breakfast or lunch, and will only eat a small portion of his dinner, but he will only eat his dinner in his room. He drinks a lot of water, but he doesn't really eat. I know working out and exercising is really good, but to not be getting hardly any nutrition is scarring me. Am I worrying for nothing?