I've been on a diabetes drug called metformin (Glucophage) since soon after starting clozaril which is known for heavy weight gain. The metformin seemed to stop my weight from going up any further and when I started trying to lose weight I have been able to do that too (and I assume the metformin helps). I agree with the other posters that being on the lowest possible dose is also important. You can always increase the dose if needed and stay at a lower dose when it isn't (I haven't succeeded at this myself but in theory it's a good idea).