Prozac (Fluoxetine) and Weight Gain

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Antidepressants have long been associated with weight gain. When Prozac (fluoxetine) first arrived on the scene in 1988, many doctors and patients were hopeful that it might alleviate this problem.

Unlike older antidepressants, such as the tricyclics (TCAs) and monoamine oxidase inhibitors (MAOIs), Prozac affects mainly serotonin receptors. Because of this, it was hoped that it wouldn't have the same adverse effects, such as dry mouth, drowsiness, and weight gain.


Unfortunately, it didn't quite work out that way. While Prozac doesn't have side effects that are as severe as the older antidepressants, it did emerge over time that weight gain could still be a problem.

Although many patients initially do maintain or even lose weight during the first few months on Prozac, a small percentage of people eventually gain weight, especially with long-term use, which means longer than six months.

Prozac is not alone in causing this potential dreaded side effect; many antidepressants can potentially lead to weight gain, particularly with long-term use. In fact, Prozac is actually considered one of the weight-neutral antidepressants, meaning it doesn't typically cause weight gain.

Why It Causes Weight Gain

It's not known for certain why Prozac and other antidepressants may cause weight gain, although it's possible that they may somehow affect your appetite or metabolism. Some people may gain weight while taking Prozac simply because they were not eating well while they were depressed and the antidepressant has caused their normal appetite to return. It can be difficult to pinpoint the exact reason for weight gain when you're taking an antidepressant.

What You Can Do

Unfortunately, there is no magic bullet to help you lose weight you may have gained while taking Prozac. The same options for weight loss exist as for those who have gained weight for other reasons, including:

  • Implementing a healthy diet
  • Engaging in regular exercise, which has the added benefit of naturally boosting your mood
  • Weight loss drugs

Other Options

If none of the above work for you, another option is to ask your healthcare provider about changing to a different antidepressant. Certain antidepressants are less likely to cause weight gain than others. For example, the atypical antidepressant Wellbutrin (bupropion) is linked to weight loss.

Keep in mind that different people often respond in different ways to the same medication, so another antidepressant may work better for you in treating your depression while not causing you to pack on the pounds.

2 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Cascade E, Kalali AH, Kennedy SH. Real-World Data on SSRI Antidepressant Side Effects. Psychiatry (Edgmont). 2009;6(2):16-8. PMID:19724743

  2. Nihalani N, Schwartz TL, Siddiqui UA, Megna JL. Weight gain, obesity, and psychotropic prescribing. J Obes. 2011;2011:893629. doi:10.1155/2011/893629

Additional Reading
  • Weil A. Why Do Antidepressants Cause Weight Gain?  Andrew Weil, M.D. Healthy Lifestyle Brands, LLC. Published February 11, 2011.

  • Blumenthal SR, Castro VM, Clements CC. An Electronic Health Records Study of Long-Term Weight Gain Following Antidepressant Use. Journal of the American Medical Association. August 2014;71(8):889–896. doi:10.1001/jamapsychiatry.2014.414.

By Nancy Schimelpfening
Nancy Schimelpfening, MS is the administrator for the non-profit depression support group Depression Sanctuary. Nancy has a lifetime of experience with depression, experiencing firsthand how devastating this illness can be.