Hello labelleliason, I am currently on Anafranil , and am of course bi-polar. Initially I was worried just like you, O great another 20 lbs , right? But it didn't happen on this drug for me! I know that doesn't reassure you that much, but at least you're not alone. My psychiatrist is a brilliant man (has so many degrees behind his name it takes up two lines of an envelope LOL) and the reasoning for this medication for me and my condition, is that I find sometimes when mania hits, I become analytical to the point of obsessive, I'd have unwanted thoughts and toil of them for hours keeping me up nights and days until I didn't which was which.
Definitely not saying this is the case for you, and if you do not have faith in your doctor a second opinion or a referral is in order, but if you are displaying symptoms such as above, you may want to give it a shot.