The Link Between Antidepressants and Weight Gain Explained

Around 14% of American adults take antidepressant medication, which may be prescribed for major depressive disorder and other mental health conditions like anxiety. For some people, these medications result in weight gain that begins several months after beginning treatment.

Unfortunately, there’s much that remains unknown about why antidepressants can cause weight gain.  It may occur because the brain chemicals affected by antidepressants also influence appetite and food choices. It could also be linked to a positive change in mood, a person’s genetics, or other factors that play a role in body composition.

However, not everyone who takes these medications will notice a change in their weight, and the risk of weight gain varies across different types of antidepressants.

This topic is complex and can be confusing, especially since more research is necessary to fully understand exactly how antidepressants affect weight. In this article, we’ll demystify the topic and review what we know about why weight gain occurs with antidepressants, which types cause the most weight gain, and strategies for minimizing weight changes.

Introduction to Antidepressants and Weight Gain

Numerous studies have found an association between long-term use of antidepressants and changes in body weight, but the story here is complicated.

It is rare for an antidepressant to cause weight gain in the short term. However, most people who are diagnosed with depression are prescribed to take these drugs for many months or years, which can eventually lead to noticeable changes in weight.

When it occurs, weight gain usually starts after at least four to six months, and the gain typically ranges between 2 and 15 pounds.

This weight gain doesn’t affect everyone, though. In addition, not all antidepressant drugs have the same potential to influence weight. In fact, one antidepressant has been consistently linked with weight loss.

Before delving deeper into why antidepressants may affect weight, it may help to review the main types of antidepressants available for doctors to prescribe and their connection to weight gain.

It is rare for an antidepressant to cause weight gain in the short term. However, most people who are diagnosed with depression are prescribed to take these drugs for many months or years, which can eventually lead to noticeable changes in weight.

Main Classes of Antidepressants

Antidepressants work by modifying levels of certain chemicals in the brain called neurotransmitters. There are multiple ways that drugs can affect neurotransmitters, which is why there are many different antidepressant medications.

The most commonly prescribed antidepressants are designed to increase levels of the neurotransmitter serotonin, which plays a vital role in mood and state of mind. 

Selective serotonin reuptake inhibitors (SSRIs) work to raise serotonin levels. Specific SSRIs include:

• Sertraline (Zoloft)
• Fluoxetine (Prozac)
• Paroxetine (Paxil)
• Escitalopram (Lexapro, Cipralex)
• Citalopram (Celexa)
• Fluvoxamine (Luvox)

Another group of antidepressants called serotonin-noradrenaline reuptake inhibitors (SNRIs) affect the neurotransmitters serotonin and norepinephrine. Examples include drugs like:

• Venlafaxine (Effexor)
• Duloxetine (Cymbalta)
• Mirtazapine (Remeron)
• Desvenlafaxine (Pristiq)

SSRIs and SNRIs can cause weight gain, but some of these drugs, such as paroxetine, have been associated with much more significant increases in weight.

Atypical antidepressants also affect neurotransmitters but in ways that are distinct from SSRIs or SNRIs. These drugs can include:

• Bupropion (Wellbutrin), which affects dopamine, a chemical in the brain that helps control pleasure and reward
• Nefazodone (Serzone), which operates differently to modulate serotonin

Bupropion is an especially interesting case because it has actually been associated with weight loss, not weight gain. Interestingly, unlike most other contemporary antidepressants, it doesn’t target serotonin.

Substantial weight gain was more common with earlier generations of antidepressants. Today, these types of drugs are usually only prescribed when other treatments have not been effective. These classes of antidepressants include:

• Tricyclic antidepressants (TCAs), including amitriptyline (Elavil), desipramine (Norpramin), and nortriptyline (Aventyl, Pamelor)
• Monoamine oxidase inhibitors (MAOIs), including tranylcypromine (Parnate) and phenelzine (Nardil)

The evolution of antidepressant medications has generally reduced the number and severity of side effects and made it easier for people with a mental health condition to continue taking their prescribed pills for an extended length of time.

Basic Mechanisms of Antidepressant-Induced Weight Gain

Although there are multiple studies linking antidepressants to weight gain, researchers still don’t fully understand the mechanism behind why this happens.

One open question among experts is whether weight gain happens as a direct side effect of an antidepressant drug or if it is a downstream consequence of an improvement in depressive symptoms.

There are a number of potential ways that antidepressants may influence body weight. One main reason it may occur is because neurotransmitters like serotonin don’t just affect mood. They also influence appetite, stress, sleep, and other elements of health.

Although more data is needed to draw conclusions, research to date offers some clues about why antidepressants may cause weight gain.

Impact on Hunger and Appetite

Appetite is largely regulated by hormones that can be impacted by changes in neurotransmitters. The result may be an increased drive to eat. Over time, this can lead to overeating and taking in excess calories, culminating in weight gain.

Appetite changes may also occur as a result of effective treatment for depression. If depression is causing a lack of appetite, an improved mood may account for greater food intake.

Carbohydrate Cravings

In addition to an increased overall appetite, some evidence suggests that people taking antidepressants may have cravings for foods that are high in carbohydrates, such as pasta, bread, and sugary snacks. Eating too many of these foods can play a role in weight gain.

Effects on Insulin Sensitivity and Blood Sugar Levels

Insulin is a hormone that works to regulate blood sugar levels in the body. Some research has found that antidepressants can modify activity in parts of the brain that are involved in insulin signaling. If normal processes of insulin production are disrupted, it may affect metabolism. In particular, it may play a role in insulin resistance, which can lead to higher blood sugar levels and is a precursor to diabetes.

At the same time, it is important to note that untreated depression is associated with an increased risk of developing type 2 diabetes. Some research has suggested that, in people who already have type 2 diabetes and depression, antidepressants may offer beneficial outcomes for overall health.

Psychological Factors and Emotional Eating

A person’s mood and emotional wellness can impact when, what, and how much they eat. One of the benefits of depression treatment is the ability to enhance a person’s mood. In changing the way that they feel, these drugs may effectively alter dietary patterns.

Another way to think about this possible mechanism is that instead of antidepressants causing unwanted weight gain, they may be reversing unwanted weight loss that can occur during depressive periods.

Genetics

Genetic variation is another possible explanation for the fact that not everyone gains weight when taking an antidepressant. Individual genes may make certain people’s bodies respond to antidepressants in ways that make them more susceptible to weight gain.

Other Factors Affecting Body Weight

Of course, body weight isn’t simply determined by the medication that someone takes. Numerous lifestyle choices play a critical role in body composition. Evidence points to greater risks of weight gain among people who take antidepressants and have unhealthy habits related to diet, sleep, and physical inactivity.

Weight gain also tends to occur in most people as they enter adulthood and middle age, regardless of whether they take antidepressants.

The Potential Impacts of Weight Gain

While a small amount of weight gain may not be an issue for some people taking antidepressants, for others it can be a cause for more serious concern.

Weight gain can affect a person’s self-image, and some people may discontinue the use of an antidepressant in order to limit perceived weight gain. Abruptly stopping the use of these drugs can have profound and sometimes dangerous effects on mental health.

For some users of antidepressants, substantial weight gain may contribute to obesity. Having obesity is associated with elevated risks of numerous health issues, including high blood pressure, cardiovascular diseases, and metabolic disorders like diabetes.

Which Antidepressants Cause the Most Weight Gain?

Based on recent research, it is believed that the drugs paroxetine and escitalopram are most likely to cause weight gain.

Modern antidepressants, including SSRIs and SNRIs, are generally regarded as causing less weight gain than older drugs. Among the newer medications, though, there is considerable variability in how they impact weight.

A recently published study has shed more light on which drugs cause the most and least weight gain. In what is known as a cohort study, the authors analyzed medical records of over 180,000 people taking different antidepressants to see how their weight changed over time.

On average, they found that two drugs, bupropion and fluoxetine, were actually associated with weight loss, and the drug sertraline had a neutral effect on weight. The drugs paroxetine and escitalopram were found to be tied to the most weight gain.

1. Bupropion (difference: -0.48 pounds)
2. Fluoxetine (difference: -0.15 pounds)
3. Sertraline (difference: 0 pounds)
4. Citalopram (difference: 0.26 pounds)
5. Venlafaxine (difference: 0.37 pounds)
6. Duloxetine (difference: 0.75 pounds)
7. Paroxetine (difference: 0.81 pounds)
8. Escitalopram (difference: 0.90 pounds)

As you can see in the data, the average amount of weight loss or gain was quite small across the entire study population. However, people taking paroxetine or escitalopram had a roughly 15% greater likelihood of gaining a more significant amount of weight compared to people taking the other antidepressants in the study.

This study certainly isn’t the final word on how these drugs stack up when it comes to weight loss, but it does offer insight that may help doctors and patients when choosing among prescription antidepressants.

Do Any Antidepressants Cause Weight Loss?

Several studies have found that the drug bupropion is associated with weight loss rather than weight gain. This antidepressant is in a class by itself because it does not act on the brain’s serotonin system. Combined with its mild stimulant effect, this may explain the weight changes linked to bupropion.

However, a downside of this drug is that some people find that it increases anxiety, a problematic side effect for people with mental health conditions.

Choosing an Antidepressant

Many antidepressants have comparable effectiveness, which means that your doctor or psychiatrist can choose among multiple options to recommend the best option for your care.

They may start by reviewing your health history and emotional well-being. If you’ve taken an antidepressant before, they may ask for details about that drug and dosage and your response to it.

Your doctor may ask questions about side effects and any concerns you have about how they may affect your quality of life. If weight management is an important issue for you, make sure to bring it up with your provider. They can take all of this information into consideration and give detailed advice about which antidepressant may best suit your situation.

After making a prescription, expect to have a plan for ongoing follow-up. That provides an opportunity to see how well the therapy is working, review the dose, and suggest a substitute medication if the initial antidepressant isn’t working or is causing unwanted side effects like weight gain.

Managing Weight Gain While on Antidepressants

Various strategies and tips may be helpful to reduce weight gain when taking an antidepressant.

• Try to find time for regular physical activity, which doesn’t have to mean intense exercise.
• Consider your nutrition and diet, and make changes where you can to include foods that are healthy and nourishing.
• Limit excess consumption of alcohol.
• Work to develop good sleep habits and eliminate sources of sleep disruption. Talk with your doctor if you experience symptoms of insomnia

Mindfulness about these habits can often encourage overall wellness and better weight management. When modifying health habits, though, it’s best to collaborate with a healthcare provider who can address the safety of different options and which are the top priorities in your situation.

Your doctor may also be able to refer you to a nutritionist, physical therapist, sleep specialist, or other provider for a consultation. These tailored services may help you identify a practical strategy for maintaining a healthier weight when taking an antidepressant.

Future Research Directions

While we know that antidepressants can influence body weight, there is a great deal that is still unknown about why this occurs and how to address it.

Researchers are working to obtain new information about the ways that different antidepressants affect the brain and body. This work promises to shed light on not only the incidence of weight gain and other side effects but also how these side effects impact specific populations, including women, adolescents, children, and people with certain gene variants.

In the meantime, it’s important to recognize that while weight gain can occur, it isn’t a given. Many patients experience little or no weight gain, which can be related to the specific antidepressant that they are prescribed. Working with an experienced doctor or psychiatrist can enable people with depression to get personalized care for their condition and for any side effects of treatment.

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