Di thyroid problem or prozac (fluoxetine) side cause me to gain 40 lbs in a year?

Check labs: It is imortant to check you thyroid funtion test before you start any antidepressant. In general the data and clinical experience show that Prozac (fluoxetine) is causing weight loss during the short term use such as a year, which is why it is approved at the doses of 60-80 mg for bulimia nervosa binge eating, but on a long run it can cause weight gain.