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  • Mental Health Issues
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  • What Are Antidepressants?What Are Antidepressants?
  • Can It Cause Weight Loss?Can It Cause Weight Loss?
  • Why Is It Causing Weight Loss?Why Is It Causing Weight Loss?
  • When It Becomes a ProblemWhen It Becomes a Problem
  • PreventionPrevention
  • When to Talk to Your DoctorWhen to Talk to Your Doctor
  • ConclusionConclusion
  • Additional ResourcesAdditional Resources
  • InfographicsInfographics

Does Prozac Cause Weight Loss? Everything You Need to Know

Eric Patterson, LPC

Author: Eric Patterson, LPC

Eric Patterson, LPC

Eric Patterson LPC

Eric has over 15 years of experience across all age groups focusing on depression, anxiety, personality disorders, and substance use disorders.

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Headshot of Kristen Fuller, MD

Medical Reviewer: Kristen Fuller, MD Licensed medical reviewer

Headshot of Kristen Fuller, MD

Kristen Fuller MD

Kristen Fuller, MD is a physician with experience in adult, adolescent, and OB/GYN medicine. She has a focus on mood disorders, eating disorders, substance use disorder, and reducing the stigma associated with mental health.

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Published: May 19, 2022
  • What Are Antidepressants?What Are Antidepressants?
  • Can It Cause Weight Loss?Can It Cause Weight Loss?
  • Why Is It Causing Weight Loss?Why Is It Causing Weight Loss?
  • When It Becomes a ProblemWhen It Becomes a Problem
  • PreventionPrevention
  • When to Talk to Your DoctorWhen to Talk to Your Doctor
  • ConclusionConclusion
  • Additional ResourcesAdditional Resources
  • InfographicsInfographics
Brand name:
Prozac
Generic name:
Fluoxetine
Is the generic available:
Yes
Class of drug:
SSRI
FDA-approved treatments:
Major Depression, OCD, Bulimia Nervosa, Panic Disorder
Common Off-label Uses (non-FDA approved):
Body Dysmorphic Disorder, Generalized Anxiety Disorder, Social Anxiety Disorder, PTSD, Disruptive Mood Dysregulation Disorder, Borderline Personality Disorder, specific phobias
Common alternatives:

Zoloft, Lexapro, Paxil

View Drug Class, FDA-Approved Uses, Off-Label Uses, and more

*An off-label use of a medication is a use that is not FDA-approved. Prescribers can decide to use a medication off-label because, in their professional judgment, they believe it may offer a benefit to someone.

Unlike other medications that trigger weight gain as a potential side effect, Prozac may actually create a short-term reduction of weight. It is unclear whether the weight change is a direct result of the medication or an indirect impact from changing levels of depression and anxiety.

If you want to discuss your current prescription with a provider or are considering a prescription for Prozac, an online psychiatry platform can be a good place to start. Talkiatry and Brightside Health offer psychiatric assessments and prescription consultation, and can address concerns about potential weight changes while taking Prozac.

Boxed Warning: Fluoxetine (Prozac) - Risk of suicidal thoughts and behaviors in certain people

Click here to open and close the box warning container.

Fluoxetine, the active ingredient in Prozac, has a black box warning. These are the most serious types of warnings from the Food and Drug Administration (FDA). Fluoxetine can increase the risk of suicidal thoughts and behaviors in children, adolescents, and young adults. Regardless of your age, you should talk with your doctor about serious risks with fluoxetine and any other medications before starting treatment.

What Are Antidepressants?

Antidepressants are a broad class of medications that work primarily totreat the signs and symptoms of various types of depression. These medications for depression modify the chemical messengers in the brain to target the effects of depression and promote well-being.1 Contrary to what the name suggests, professionals prescribe antidepressants for concerns other than depression.

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Antidepressants can also help treat:1,2

  • Other mood disorders like bipolar disorder
  • Anxiety disorders like panic disorder
  • Eating disorders
  • Post-traumatic stress disorder (PTSD)
  • Pain
  • Insomnia

There are many types of antidepressants. Each group works differently by interacting with a specific neurotransmitter or group of neurotransmitters. Prozac (fluoxetine) is a selective serotonin reuptake inhibitor (SSRI). It treats mental health conditions by blocking the reabsorption of serotonin, so more is available in the brain.

Other antidepressants, like Effexor (venlafaxine), are serotonin and norepinephrine reuptake inhibitors (SNRIs). These medications affect the reabsorption of norepinephrine and serotonin.1

Can Antidepressants Cause Weight Loss?

As a class of medications, antidepressants are known to trigger changes in weight. Most frequently, these medications are associated with weight gain, but on occasion, weight loss may also occur. Prozac is linked to weight loss, especially early in treatment.3,4 Studies show that when people begin treatment with Prozac, they could experience a modest weight loss of about one pound.

This weight loss will be observable about one month after beginning treatment. The weight loss will not be permanent, but it seems to continue throughout the first three months of treatment with Prozac. Like other medication results, not everyone will lose weight on Prozac. Of those studied, though, the weight loss was fairly consistent.

When researchers tracked patients for six months and more, the people gained back the original weight. In some cases, they added an average of six pounds in the year after starting treatment.3,4 Although this may seem significant, the weight gained on Prozac is comparable or lower than similar antidepressants. Antidepressants are more often related to weight gain rather than weight loss.

Antidepressants that cause weight loss may include:

  • Prozac (fluoxetine)
  • Wellbutrin (buprinopine)

Like Prozac, Wellbutrin seems associated with short-term weight loss. At the 3-month mark, patients report some weight loss on average. Then, weight seems to increase slightly at 6-month and 9-month reviews. By the one year mark, average weight is similar to the original baseline levels.3

Antidepressants & Weight Gain

The more common effect of antidepressants is to trigger weight gain in patients. Some gains may be immediate, delayed, continuous, or temporary with plateaus. Older medications are more strongly linked to weight gain and other unwanted effects, but even the newest generations of antidepressants may produce weight gain.

Antidepressants that cause weight gain may include:3,5

  • Amitriptyline, Tofranil (imipramine) and doxepin: types of tricyclic antidepressants
  • Nardil (phenelzine) and other monoamine oxidase inhibitors (MAOIs)
  • Paxil (paroxetine) and Celexa (citalopram): two types of selective serotonin reuptake inhibitor
  • Effexor (venlafaxine): a commonly used serotonin and norepinephrine reuptake inhibitor
  • Remeron (mirtazapine): an atypical antidepressant

Some medications cause weight gain that seems to level out over the course of a few months. Other medications, like Effexor (venlafaxine) and Remeron (mirtazapine), seem to trigger weight gains that continue to increase with time.1

The primary goal of antidepressants is to manage the patient’s mental health symptoms, but a rapid weight gain could prove problematic, especially if the person is already overweight at the beginning of treatment. The decision to continue or end treatment must be a conversation between the prescriber and the patient as they consider the risks and benefits of continued treatment.

Why Does Prozac Cause Weight Loss?

No one can state with precision why some antidepressants trigger weight gain and why others, like Prozac, seem to produce weight loss. Much of the impact has to do with individual differences, depressive symptoms, and expected weight gain in adults.

The weight changes during depression and anxiety are complex situations. Some people will note decreased appetite with weight loss that follows when symptoms are high. Others will find that high symptoms are linked to increased appetite and weight gain.4

The weight loss that comes with Prozac could be a sign that depression is alleviating. As symptoms reduce, the overeating and weight gain that comes with it begins to fade. This change allows people to lose some depression-related weight.5

The decreased depressive symptoms could also spark an increase in energy and motivation. With more physical activity, the person could shed some weight in the early months of Prozac treatment.

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When Prozac Weight Loss Becomes a Problem

Significant weight loss is a concern when people use Prozac. The concern is more troubling when it occurs in very underweight people who are depressed or living with bulimia nervosa, an eating disorder.6 A person with an eating disorder could continue to lose weight because the Prozac treatment is not doing enough to manage symptoms.

Among people treated with Prozac for bulimia nervosa, 8% experienced decreased appetite. Among those with depression, 11% experienced decreased appetite. Among those with obsessive-compulsive disorder (OCD), 17% experienced decreased appetite.6

If you find that you or a loved one are losing significant weight, make a call to the prescriber or primary care physician. They can assess the severity of the weight loss and recommend appropriate care to lower the risk.

How to Prevent Prozac Weight Loss

At the beginning of your treatment with Prozac, have a conversation with your doctor about the risks and benefits. Discuss the potential for weight loss, what you should do about it, and when to be concerned with the impact. Preventing Prozac weight loss may not be the most important goal. Instead, it could be a better decision to focus on improving your mental health concerns.

Consider weighing yourself weekly to assess and track any changes in your weight. Then, work with your prescriber to note when weight loss could become problematic.

If weight loss continues, work with your doctor to:

  • Change the dose: the amount of Prozac you take could result in more weight loss. The prescriber may increase or decrease as needed to minimize unwanted changes.
  • Switch medications: if the side effects are too great, another medication may be the best course of action.
  • Shift your diet and exercise routines: take some time to reflect on your habits to see if you can adjust your intake or physical activity to slow the weight loss.
  • Work with professionals: dietitians and personal trainers can use their expertise to manage your weight. Trusting their education and experience can help reduce the effects of Prozac.

When to Speak With Your Doctor

Any time you are using Prozac to manage symptoms of depression, anxiety, or another condition, you should have consistent communication with your doctor. From the first dose to the most recent refill, having an open and honest dialogue to minimize the risk of side effects. It can also help you catch problems early.

At any point of your treatment, you could benefit from asking your doctor questions that address your concerns and improve your safety. Your doctor should patiently answer your questions and relieve your worries.

Consider asking your doctor these questions:1

  • Why do you think Prozac is best for me?
  • What are the possible side effects of antidepressants?
  • Do I need to change my diet or exercise while taking this medication?
  • How do people usually respond to this medication?
  • What should I do if I begin experiencing side effects for this medication?
  • What type of weight changes should I expect from this medication?
  • Is it safe to take Prozac and Adderall together?

Final Thoughts

While Prozac’s side effects may include weight loss for some, every individual responds differently. It’s important to speak with your doctor about any side effects you may have and how to best manage them. Most often, the weight loss will be moderate before you return to your starting weight several months after treatment begins. It should dissuade you from trying Prozac to manage your mental health.

Additional Resources

To help our readers take the next step in their mental health journey, Choosing Therapy has partnered with leaders in mental health and wellness. Choosing Therapy is compensated for marketing by the companies included below.

Virtual Psychiatry

Circle Medical – Anxiety and Depression Treatment. Meet with an online doctor today! All prescriptions are based on necessity determined by a medical professional. Diagnosis and prescription over video. Insurance accepted. No membership or hidden fees. Same day appointments. Visit Circle Medical

Talkiatry – Get help from a real doctor that takes your insurance. Talkiatry offers medication management and online visits with expert psychiatrists. Take the online assessment and have your first appointment in days. Free Assessment

Therapy for Anxiety & Medication Management

Brightside Health – develops personalized plans that are unique to you and offers 1 on 1 support from start to finish. Brightside Health accepts United Healthcare, Anthem, Cigna, and Aetna. Appointments in as little as 24 hours. Start Free Assessment

Talk Therapy

BetterHelp – Get support and guidance from a licensed therapist. BetterHelp has over 30,000 therapists who provide convenient and affordable online therapy.  BetterHelp starts at $65 per week and is FSA/HSA eligible by most providers. Take a Free Online Assessment and get matched with the right therapist for you. Take free assessment

Anxiety Newsletter

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For Further Reading

  • Harvard Health: “Antidepressants cause minimal weight gain”
  • MedlinePlus Drug Information: Fluoxetine
  • NHS: “Side effects of fluoxetine”

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Online psychiatry, sometimes called telepsychiatry, platforms offer medication management by phone, video, or secure messaging for a variety of mental health conditions. In some cases, online psychiatry may be more affordable than seeing an in-person provider. Mental health treatment has expanded to include many online psychiatry and therapy services. With so many choices, it can feel overwhelming to find the one that is right for you.

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Prozac & Weight Loss Infographics

Does Prozac Cause Weight Loss Antidepressants and Weight Gain Why does Prozac Cause Weight Loss

How to Prevent Prozac Weight Loss

Sources

ChoosingTherapy.com strives to provide our readers with mental health content that is accurate and actionable. We have high standards for what can be cited within our articles. Acceptable sources include government agencies, universities and colleges, scholarly journals, industry and professional associations, and other high-integrity sources of mental health journalism. Learn more by reviewing our full editorial policy.

  • (2016, October). National Institute of Mental Health. Mental Health Medications. Retrieved from https://www.nimh.nih.gov/health/topics/mental-health-medications

  • (2020, December). National Alliance of Mental Illness. Fluoxetine (Prozac). Retrieved from https://www.nami.org/About-Mental-Illness/Treatments/Mental-Health-Medications/Types-of-Medication/Fluoxetine-(Prozac)

  • Michelson, D., Amsterdam, J., et al. (1999, August). Changes in Weight During a 1-Year Trial of Fluoxetine, American Journal of Psychiatry. Retrieved from https://ajp.psychiatryonline.org/doi/pdf/10.1176/ajp.156.8.1170

  • Blumenthal, S., Castro, V., Clements, C., et al. (2014). An Electronic Health Records Study of Long-Term Weight Gain Following Antidepressant Use. JAMA Psychiatry. Retrieved from https://jamanetwork.com/journals/jamapsychiatry/fullarticle/1878922

  • Hall-Flavin, D. (2018, November 17). Antidepressants and Weight Gain: What Causes It? Mayo Clinic. Retrieved from https://www.mayoclinic.org/diseases-conditions/depression/expert-answers/antidepressants-and-weight-gain/faq-20058127

  • (2021, December 23). DailyMed. Prozac – Fluoxetine Hydrochloride Capsule. Retrieved from https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c88f33ed-6dfb-4c5e-bc01-d8e36dd97299

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