I haven't experienced weight gain due to bipolar meds, but I have with migraine preventative medicine. The good thing is that the medicine doesn't magically cause weight gain, it causes hunger or craving, which trigger overeating and weight gain.

You've won the biggest battle, you are aware. I would suggest that the first thing that you do is journal your eating. Right down every little thing that goes into your mouth. This will make you very aware of your eating habits, you will also be able to see if there are any particular times of the day that really give you problems. For example, if you come home from work everyday and go straight to the kitchen and snack, you can try coming home and going straight to your bedroom and changing cloths to break the habit.

You all may want to discuss with your doctor if there are alternative medicines that you can try that are less likely to promote overeating. For me, after trying many migraine medicines, I decided that reduced migraines was worth the extra 10 pounds that I personally had gained.