I'm bipolar II with major anxiety and am afraid I had serious weight gain. I was on 600mg for about 8 years. I put on about 70 pounds in the first couple years. Somehow managed to lose most of it and then put back on 80. As someone else mentioned it gave me insane cravings. I was so ravenous at night, if nothing else had been available, I think I would have eaten cardboard. And this from someone who had never had any weight issues previously. I always tended to be on the low side of "normal" in weight.

That said, it probably saved my life at the time. It stopped my obsessive, cyclical negative thinking. I would have a nasty memory come up and it would just cycle through my head non-stop. It also did help keep my lows from getting nearly as bad and helped with anxiety and sleep.

The only way I was able to lose weight when taking it was a low carb diet, with mostly natural foods, keeping preservatives and such to a minimum.
I'm currently slowly weaning off the Seroquel for lots of reasons. I'm on that good (for me) diet and exercising and had started losing weight, slowly, before I began weaning off. However, the lower my dose gets, the faster my weight drops.