Either drug can cause weight gain, but Prozac generally doesn't cause weight gain until about four to six months into taking it.

That's the bad news, you could talk to your doctor about trying Topomax with them, that might help minimize the weight gain.

And skipping a few days of Prozac won't do a thing for you. It can take a while to get your body back to pre-SSRI metabolism.

For what it's worth, Zoloft or Wellbutrin might be easier on teh weight gain. Then again, if Prozac is working for you, much better to work with your pdoc to mitigate the weight gain. Which, in my opinion, is more probably the Risperdal anyway.