Yes there is a co-relationship between Risperidone and Concerta/Ritalin/methylphenidate.
They CAN work well together, but it takes a sharp psychiatrist, and a bit of tuning.
The Concerta may be too high a dose, over-suppressing appetite during the day and then when it wears off, adding to the hunger.
Or, it may be that the Concerta just wears off... and the hunger comes roaring back.
In either case, a small top-up dose of short-acting Ritalin (or equivalent) can keep the edge off the hunger.
With Risperidone, one of the tricks is to NEVER let them get hungry in the first place.
Plan meals and snacks from wake to bed-time, no more than 2-3 hours between (shorter if physically active).
If they are that hungry, each meal and snack needs to include protein, fat, and slow-acting carbs. Include quality fast-acting carbs at times when you know they will need an extra boost (just before or just after PE, for example).
Get them eating by the clock, plan the calories across the day... it makes it easier to mentally turn down the hunger when you know that it's only "x" minutes to the next food.
The trouble with getting really hungry when on Risperidone is that it sends your blood sugar absolutely wonky. It can take weeks to get back on an even keel.
If you want to challenge the weight gain (and other issues) more creatively, try testing out some of the alternative diets... but not all at once, you need to know what works and what doesn't. CF (casein free), girlfriend (gluten free) and wheat free are three options. Also consider dropping anything with food dye in it, as a test - no diff for my kids, but for others it's HUGE.
Getting them to eat more veggies... we started a small "kitchen garden" and... the kids declared that having tasted that stuff (compared to store-bought), they were prepared to eat salad every single day all summer... but not the store-bought stuff, because it doesn't taste right.
