JL, I was (and am still taking) Olanzepine.
It is first and foremost an anti-psychotic drug as opposed to an anti-depressant. That sounds harsh but in reality it just slightly dulls your OMG OMG OMG shriekvoice telling you to "AVOID, RUN, HIDE!!"
You'll find you initially gain a little, but not for the reason you might think. Truth is, the drug doesn't "nyuk nyuk, fatten you up, evil drugs!!" - but because you literally stop fretting so much over eating normal amounts, and your body takes the opportunity to rebuild your poor wrecked, neglected frame.