Prozac for Weight Gain And Loss: How Fluoxetine Affects The Body

Last Updated: June 24, 2020

Authored by Roger Weiss, MD

Reviewed by Michael Espelin APRN

Prozac uses involve treatment of obesity and depression. It alleviates depression by preventing serotonin, a mood-stabilizing neurotransmitter, from being reabsorbed by the neurons. It has been shown to cause weight loss initially, but many people end up gaining weight, which can be one of the unpleasant side effects of Fluoxetine, and turning to a professional is the best way to cope in this case.

Does Prozac Cause Weight Gain? Benefits and Risks

Fluoxetine is an antidepressant, and it causes weight gain to the extent that loss of it is a symptom of depression, but the opposite is also true – it will cause loss if weight gain was a symptom of depression. It does this by maintaining a balance of serotonin, which modulates sleep, mood, and sensations of pain among other metabolic processes. Patients who have not been taking it long initially experience a loss of appetite, but their mass tends to increase over the course of time. Prozac structure and ingredients do not cause weight gain directly; however, recovery from depression can go along with weight gain because it results in improved appetite. People become more social, and this also contributes to greater food intake. If one is concerned about weight gain, they are advised to follow the instructions of a physician regarding lifestyle changes or have their medication changed.

Does Prozac Cause Weight Loss?

Alternatively, does Prozac make one to lose weight? Researchers report that patients taking it can lose up to twice as much as those taking alternative medication, such as Xenical and Meridia. A study showed patients on Fluoxetine lost 13 pounds, more than twice as much as those on Xenical (6 pounds) in the same time frame. Likewise, patients taking Fluoxetine for 27 weeks on average lost 11 pounds, compared with less than 10 by patients using Meridia in the same period. It is important to start reducing the dose as appropriate in cases where the drug has been prescribed for obesity.
woman measuring her waist with measuring tape
Fluoxetine Weight Loss: Facts
Experts have not established how Fluoxetine helps to reduce mass exactly, but at any rate, obesity is an independent risk factor linked to the significant increase in mortality and morbidity, and its effective treatment is crucial. The Prozac dosage for weight loss is 40 mg a day, ideally. In a clinical trial study on 201 overweight or obese individuals (BMI between 25–42), participants received this dosage per day for 2 months. Progress was measured after the 4th and 8th week of administration and a month after the end of treatment. The vast majority of participants had lost an average of 7 pounds after a month and 14 by the end of the study. No gain was observed at the end of the month following discontinuation of the medication. Researchers conclude that Fluoxetine is a safe and effective drug for short-term obesity treatment. However, drinking on Prozac can impede weight loss process because spirit drinks are usually high in calories.
1.4% of study participants who took Prozac for major depression during U.S. clinical trials reported weight loss and 11 percent reported reduced appetite. Of the participants in the study who received a placebo, only 2 percent reported reduced appetite and 0.5 percent informed that their weight had dropped. However, no proof was provided whether the results would be sustained over the long term. Experts suggest that physical activity combined with a healthy diet is the best way to control body mass and prevent obesity.

Going Off Fluoxetine: Talk to a Doctor

It is important to speak with a physician if one wants to stop Prozac. A competent doctor will give his or her patient detailed instructions on how to taper off it to avoid withdrawal symptoms like sleeplessness, irritability, dramatic weight loss or gain, fatigue, headaches, confusion, and vertigo. These symptoms can persist for up to two months.
Apart from causing dramatic weight gain or loss, fluoxetine can produce feelings of euphoria that can lead to abuse and addiction. If a person is unable to cope with the symptoms of withdrawal from Prozac or experiencing sudden body mass changes, getting professional help at a rehab center is crucial – these facilities have experienced medical staff who help people heal in a safe, welcoming environment.

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Published on: June 27th, 2018

Updated on: June 24th, 2020

About Author

Roger Weiss, MD

Dr. Roger Weiss is a practicing mental health specialist at the hospital. Dr. Weiss combines his clinical practice and medical writing career since 2009. Apart from these activities, Dr. Weiss also delivers lectures for youth, former addicts, and everyone interested in topics such as substance abuse and treatment.

Medically Reviewed by

Michael Espelin APRN

8 years of nursing experience in wide variety of behavioral and addition settings that include adult inpatient and outpatient mental health services with substance use disorders, and geriatric long-term care and hospice care.  He has a particular interest in psychopharmacology, nutritional psychiatry, and alternative treatment options involving particular vitamins, dietary supplements, and administering auricular acupuncture.


Leave a comment

  • Judy Hunt
    I recently stopped taking fluoxetine 40 mg and I seem to be retaining fluid, should I take a diuretic and if so which one.
  • Nancy O
    I started Prozac 1 wk ago 20mg for 1st wk now I start 40 mg today. How long do I have to b on it before I see any weight loss?