I'm not a psychiatrist, but my research seems to indicate that antidepressants (SSRIs, tricyclics, MAOIs) may cause weight gain in about 25% of people taking them. Paxil (SSRI) seems most likely to cause weight gain, and Zoloft (SSRI) seems least likely to cause weight gain. Nobody knows for certain why this occurs, but the leading theory is that when people become happier they are able to enjoy pleasure more, so for some people eating becomes more pleasurable. That's just a theory.

Some physicians suggest changing antidepressants every so often (don't do this unless your physician says it's okay). And you never want to take a SSRI with a MAOI because it can cause a very serious reaction called serotonin syndrome.

I would suggest you set dietary guidelines and incorporate an exercise regimen.