 [ Symptoms ] does prozac cause weight gain what about zoloft [ Disease ] selective serotonin reuptake inhibitors ssris are a class of antidepressant medications that include citalopram celexa fluoxetine prozac sertraline zoloft and several others in clinical trials these medicines did not consistently cause weight gain some people taking an ssri for two to three months lost a pound or two while others gained 5 pounds or more    but rarely were the weight changes much different than those in people taking a placebo sugar pill it can be hard to separate out any side effects of the ssri itself from the positive response to treatment for example some people with depression andor anxiety may regain their appetite as they start to feel better eat more and gain weight others may find the energy to exercise when they could not easily do so before maintaining or losing weight each person responds to ssri treatment slightly differently by devoting energy to eating right and exercising while taking an ssri you may be able to avoid unhealthy weight gain