I am on Effexor XR 300 mg and olanzapine 15 mg (+ lamotrigine and provigil). The Dr. has me on 2000 mg Metformin as well to try to offset the weight gain from olanzapine.

Before the metformin, I gained 40 lbs. (164 to 205!). Now I am losing weight (with diet and exercise) at about 1 lb/week, so I guess the metformin is doing its job. I also have a fasting blood sugar in the 80s with metformin, so the olanzapine hasn't made me diabetic.

The other side effect (but it's hard to say which drug caused it) is a total loss of my sex drive, but I don't have a partner now, so this is actually a bonus ; ) I can still have an orgasm, unlike with many SSRIs, I'm just not interested.

BUT the olanzapine works so well that the weight gain is worth it. Ask your doctor for some metformin, that's my suggestion. Good luck!