Does Prozac cause weight gain?

In this article:

• Can Prozac cause weight loss?
• Does Prozac cause weight gain?
• Other antidepressant drugs and weight gain
• Avoiding Prozac weight gain

In this article

• Can Prozac cause weight loss?
• Does Prozac cause weight gain?
• Other antidepressant drugs and weight gain
• Avoiding Prozac weight gain

Prozac (fluoxetine) is a prescription medication used for major depressive disorder (also known as depression) and other mental health conditions. It was approved by the FDA in 1987 and belongs to a group of drugs called selective serotonin reuptake inhibitors (SSRIs). People who take Prozac or who are considering starting Prozac may ask, “Will this medicine make me gain weight?” The short answer is that some weight gain is possible with Prozac; however, it tends to be less than the weight gain experienced with certain other antidepressants. Continue reading to learn more about Prozac and weight changes.

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Can Prozac cause weight loss?

Some people will lose weight while taking Prozac. The prescribing information notes that significant weight loss may occur, especially in people who are underweight and have depression or bulimia. 

In clinical trials for depression, 11% of people who took Prozac reported a loss of appetite, compared to 2% of people who took a placebo (inactive medication). About 1.4% of patients who took Prozac reported weight loss, compared to 0.5% who took placebo. 

In clinical trials for obsessive-compulsive disorder (OCD), 17% of people who took Prozac reported decreased appetite, compared to 10% of people who took placebo.

In clinical trials for bulimia, 8% of people who took Prozac reported decreased appetite, compared to 4% of people who took placebo.

Children and adolescents who take Prozac have their height and weight monitored, as the medication can affect growth rate and weight. 

Does Prozac cause weight gain?

Although some people lose weight on Prozac, others will gain weight. The good news is that weight gain is rare; the prescribing information does not list weight gain as a side effect, and another data reference notes that weight gain occurs in only one percent of patients. For those who gain weight on Prozac, how does this happen? There may be several explanations. 

A common symptom of depression is a change in appetite. Some people may eat more, while others eat less. If you are eating less due to depression, you may lose some weight. Then, once you start treatment with methods such as therapy and Prozac, you will begin to notice an improvement in symptoms after a few weeks. Your appetite may gradually return to normal, and you may start eating more, which may contribute to weight gain. 

Some people experience other side effects from Prozac, such as fatigue, drowsiness, or dizziness, especially in the first month or two while adjusting to the medicine. This may make you less likely to exercise, making you gain a small amount of weight. These side effects are often temporary and subside as you get used to the medication, and you can resume your normal exercise routine.

While different individuals have different results, some researchers note that Prozac may cause a small weight loss at first, but then, over time, some weight gain may occur. However, the weight gain may be attributed to recovery from depression (which may be associated with feeling more hungry, eating more, and gaining weight)—rather than a side effect of the medication. 

It’s important to note that the results of studies are varied, and many factors can contribute to body weight changes. 

Other antidepressant drugs and weight gain

Besides Prozac, some other examples of drugs in the SSRI class include:

• Celexa (citalopram)
• Lexapro (escitalopram)
• Paxil (paroxetine)
• Zoloft (sertraline)

Clinical guidelines note that of the SSRIs, Prozac is least associated with weight gain, while Paxil (paroxetine) is the SSRI most often associated with weight gain. A 2024 study found that Lexapro and Paxil were each associated with a 15% higher risk of weight gain than Zoloft in the first six months of treatment.

As for other types of antidepressant medications, certain medicines or drug classes are more likely to list weight gain as a common side effect, including:

• Tricyclic antidepressants (TCAs), such as amitriptyline or imipramine
• Monoamine oxidase inhibitors (MAOIs) such as phenelzine
• Remeron (mirtazapine)
• Trazodone

Some antidepressants, such as Wellbutrin (bupropion), are generally not associated with weight gain, and may even be more likely to cause weight loss. The 2024 study found that people who took bupropion were up to 20% less likely to gain weight than those who took Zoloft.

Serotonin-norepinephrine reuptake inhibitors (SNRIs) like Cymbalta (duloxetine) or Effexor (venlafaxine) often do not affect weight at all.

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How to avoid weight gain on Prozac

A bit of weight gain is not a reason to stop taking your medication. Many experts agree that the risk of not treating depression is much more serious than most possible side effects that may occur. If you experience weight gain, talk with your healthcare provider. They may have tips such as dietary changes or even trying a different medication. Here are some general tips that may help avoid weight gain on Prozac. 

• Eat a healthy diet with lots of fruits and vegetables. Stay hydrated with plenty of water. Certain foods like fruit, vegetables, nuts, and fish can help boost your mood. Limit sugar and processed foods, which can worsen mental health conditions. 
• Physical activity can help avoid weight gain and make you feel better mentally and physically. Experts recommend 150 minutes per week of moderate-activity aerobic exercise, which can be broken into smaller chunks—for example, walking for 30 minutes five times a week. Also, two days a week of strength training is recommended. Consult a healthcare provider for medical advice before beginning any new exercise program. 
• Take steps to reduce stress. Therapy is very helpful and often a recommended first treatment for many mental health conditions, including depression. 
• Other activities, such as yoga, reading a book, or meeting friends for coffee, can help reduce stress.
• Get enough quality sleep. Practice good sleep hygiene habits, such as sleeping in a cool, quiet room, removing electronics, and establishing a sleep schedule.

If these tips are too difficult to implement or do not work, you can always discuss options for different medications with your healthcare provider.