Antidepressants treat mental health conditions but can affect body weight. Although most can cause weight gain, a few antidepressants, including fluoxetine and duloxetine, may decrease appetite and lead to temporary weight loss.

Doctors commonly prescribe antidepressants to treat mental health conditions such as depression and anxiety.

Serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are second-generation antidepressants. They generally have fewer serious side effects and better tolerability than first-generation antidepressants, such as tricyclic antidepressants (TCAs).

The SSRI fluoxetine (Prozac) and the SNRI duloxetine (Cymbalta) can lead to a decrease in appetite and slight weight loss during the first months of treatment. Bupropion (Wellbutrin), which works by blocking norepinephrine and dopamine, may also have this effect.

This article explores the link between antidepressants and weight change. It also outlines other side effects and explains how to prevent weight loss.

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Weight gain is a more common side effect of antidepressants than weight loss. A 2019 review of 27 studies found that, on average, individuals experience a 5% increase in weight after starting antidepressant therapy.

Various factors could cause a person to gain weight. The possible causes include:

  • Some antidepressants increase appetite, so a person may consume more calories than their body needs.
  • When a person feels depressed, they may become less active and burn fewer calories than they consume.
  • Antidepressants may affect metabolism, causing the body to burn calories more slowly.

Some antidepressants may contribute to weight loss by decreasing a person’s appetite, leading them to consume fewer calories than they burn. In addition, mental health symptoms can affect a person’s eating habits and activity levels, and treating the underlying condition may lessen or stop these effects.

Learn about how many calories a person needs.

A few antidepressants cause no weight gain or lead to weight loss. These include:

  • Bupropion: In a 2016 study, participants who did not smoke lost an average of 7.1 pounds (lb) after 2 years of treatment with bupropion compared with those taking fluoxetine. However, those who smoked gained 2.2 lb on average.
  • Fluoxetine: A 2022 review found that in adults with overweight or obesity, taking 60 milligrams (mg) of fluoxetine daily can lead to an average weight loss of 2.7 kilograms (kg) — equivalent to almost 6 lb — during the first 6 months of treatment. There is no weight loss effect for people taking low dosages for a longer duration.
  • Duloxetine: An older 2006 study found that people taking duloxetine for major depressive disorder lost weight in the short term but gained a small amount during longer-term treatment.

It is common for side effects such as weight loss to stabilize as the body adjusts to the medication.

A 2018 study found that the use of antidepressants was associated with weight gain over at least 5 years.

The noradrenergic and specific serotonergic antidepressant (NaSSA) mirtazapine (Remeron) is most likely to cause weight gain. It is an atypical antidepressant. A 2016 study involving 36 people taking mirtazapine found that these participants gained an average of 11.6 pounds after 2 years.

The following SSRIs may cause weight gain:

Although it may result in weight loss for some people, fluoxetine (Prozac) can also cause weight gain in others. The effect of this drug on body weight may be dependent on the dosage a person receives and the duration of their treatment.

These older antidepressants may also cause weight gain:

Learn more about antidepressants that can cause weight gain.

The Food and Drug Administration (FDA) does not approve antidepressants for weight loss, so doctors do not prescribe them for this use. However, doctors do consider the potential weight change effects of medications when prescribing them.

Doctors can prescribe anti-obesity medications to help people with obesity lose weight. The options include:

People with a low or moderate weight do not need to lose weight, and excessive weight loss can be harmful. To maintain a weight within the healthy range, a person should eat a nutritious, well-balanced diet.

This involves avoiding or limiting foods high in fat, salt, and sugar, as they can increase the levels of low-density lipoprotein (LDL) cholesterol and blood glucose.

Instead, a person should try to eat meals and snacks consisting of:

  • 5 portions of fruits and vegetables daily
  • whole grain starches and carbohydrates with every meal, including oatmeal, potatoes, cereals, brown rice, whole wheat pasta, and whole grain bread
  • full-fat dairy
  • fish, eggs, poultry, meat, or other protein sources
  • 6–8 glasses of water per day, but not directly before a meal, as this may limit how much a person feels able to eat

Milkshakes with protein powder are a good way to boost calorie intake. People can also snack on nuts, peanut butter toast, yogurt, or fruit between meals.

Antidepressants may cause side effects for some people. The type and severity can depend on factors such as age, gender, and other health conditions. The side effects may lessen as the body adjusts to the medication.

The most common side effects include:

The following side effects are rare and require immediate medical attention:

If someone experiences serious side effects, they should call 911 or visit the emergency room.

If other side effects worsen or cause concern, a person should make an appointment with a doctor.

People under the age of 25 years are most at risk of suicidal thoughts when they first begin taking antidepressants. It may be wise for an individual to tell a friend or family member that they are on antidepressants so that this loved one can check in from time to time.

If antidepressants are causing concerning weight loss, it is important to contact the prescribing doctor.

Suicide prevention

If you know someone at immediate risk of self-harm, suicide, or hurting another person:

  • Ask the tough question: “Are you considering suicide?”
  • Listen to the person without judgment.
  • Call 911 or the local emergency number, or text TALK to 741741 to communicate with a trained crisis counselor.
  • Stay with the person until professional help arrives.
  • Try to remove any weapons, medications, or other potentially harmful objects if it’s safe to do so.

If you or someone you know is having thoughts of suicide, a prevention hotline can help. The 988 Suicide and Crisis Lifeline is available 24 hours a day at 988. During a crisis, people who are hard of hearing can use their preferred relay service or dial 711 then 988.

Find more links and local resources.

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Weight gain is a common side effect of antidepressants, but a few medications may cause weight loss instead. These medications include bupropion, fluoxetine, and duloxetine.

Some antidepressants may affect appetite, leading to weight changes. A person may also change their activity levels and eating habits due to mental health condition such as anxiety or depression.

Weight changes often happen in the initial months of treatment, with a person’s weight stabilizing as their body adjusts.

Doctors do not prescribe antidepressants specifically for weight loss, but they will consider an individual’s health needs when selecting a medication.

Antidepressants may cause various side effects. If a person experiences worrying or serious side effects, they should seek medical attention.