There are various meds that are weight neutral. For me they were Lithium, Lamictal, Tegretol XR, Navane, and Geodon. [Could be others I haven't tried.] I know that some other meds I was on did seem to really encourage weight gain it's hard. I'm on Seroquel XR now and that gives me trouble. But I could lose weight if I really wanted to. The hard part is finally getting that motivation to really do it. Being serious about dieting or even maintaining takes careful attention to your food input. The amount and type. Counting something is usually recommended. It hardly matters if it is points, calories, fat grams, or carbs. Most of the well-known diets work if you work them. Getting some exercise helps too. That can even help to reduce the appetite a little bit.

I don't want the above to seem like it would be "easy". It's not. Getting that motivation is hard. It's a real commitment.