I've lost 60 lbs. while on tons of meds with Weight Watchers. WW is a great program. It lets you know when you can afford a splurge and when you can't.

I'm back on it to lose even more. I was 280 lbs. at one point. Now I'm 220 and I've been keeping the weight off for a year. If WW is too expensive for you, try a calorie counting program. That would be very similar. Just make sure it's giving you ENOUGH calories. Some of them limit too much, so do your research.
I take Lithium, Trileptal, Latuda, Risperdal, and Xanax.