Ds is 13, has AS/ADHD and is prescribed methylphenidate (Ritalin). It can suppress appetite so we have to keep an eye on his weight and ensure he eats enough.
In the last few months he's stretched like elastic but hasn't had proportionate weight gain. He's 5'5" and 7st 10lb, which marks him as just underweight.
I need to find ways to get more calories into him and looking for some ideas. He's always had a limited food range because of his AS but it's widened over the last couple of years and he eats better now - nutritionally very good but socially not so good (no pizzas, burgers etc, we struggle to eat out as there's so little he'll like).
My main concern is that if I give him more calorie-laden snacks between meals (as recommended by his psychiatrist), he'll then not be hungry enough for the meals and his calorie intake overall won't change. He does eat a lot of fruit and veg with meals so I have wondered about substituting some of those for higher calorie foods like bread etc.
I'm also bothered that his current dosage is losing effect and I think it's time to increase, though his psych may be reluctant if he's not eating enough. We see him again at the end of May so I'd like to have some improvement before then.
I'd really appreciate the wisdom of MNers with similar experiences 
.
TIA