I don't have any experience with Seroquel, but the first time I went on Zyprexa I gained 25 lbs. in six weeks. That was on top of already being over 300 lbs. at the time. The last time I was put on it, it was for good, and I managed to LOSE 100 lbs. over the course of a year. My appetite was very poor because I'd lost my husband and wasn't eating. I had a bit of an increased appetite when my dose was adjusted upwards this summer, and I did put about 20 lbs. back on, but it's leveled off.