Different people respond to the same drug rather differently. Some people might not experience weight gain on Zyprexa, whereas other people might experience weight gain on Zyprexa. Same goes for all the other medications out there...

If Zyprexa is working well for your schizophrenic symptoms and the only negative side-effect is weight gain then you are (in a way) very lucky indeed. A lot of people find that they go on a medication hunt and they never really find something that works to control their symptoms.

Are there other things you could do to lose some weight? Exercise? Eat a healthier diet? I'm not sure that medication makes you gain weight so much as makes you crave certain foods and / or makes you feel lethargic so that you eat more unhealthy foods and / or don't move around as much.