Please don't rule out a medication just because somebody else says that it causes weight gain. If you look at the side effect profile for any medication, there will always be people who gained weight from it.
Also, just because a medication is known for a particular side effect, that does not mean that you will experience that side effect. For example, I was on mirtazapine/Remeron, a medication which is notorious for weight gain, yet I lost weight on it. Also, I am currently on Geodon, an atypical anti-psychotic that is known to not cause weight gain, yet I gained a lot of weight very quickly as soon as I started the medication.
If you only listen to what other people say about medications, you could be ruling out medications which could potentially help you out a great deal. And as we all know, not all medications work the same.
Yes, the weight gain side effect is a pain, but I am still on Geodon dispite the fact that it causes me to gain weight. I have made drastic changes to my diet in order to stay with this medication because when you find something that works, you'll make sacrifices to be able to stick with it. I've been able to lose the weight I gained when I first started on Geodon, and I'm able to continue to lose weight. So taking medications that cause weight gain aren't an automatic fat sentence. Good Luck!