Does Zoloft cause weight gain? Here’s what the research shows

Does Zoloft cause weight gain?

Yes, Zoloft can cause weight gain. But it’s not guaranteed, and it’s usually not a large amount when it happens.

Zoloft is a type of antidepressant called a selective serotonin reuptake inhibitor (SSRI). Like other SSRIs, it affects brain chemicals that influence mood, appetite, sleep, and energy. For some people, these shifts can indirectly influence body weight over time.

A 2024 study tracked more than 183,000 adults starting an antidepressant. Researchers found that people prescribed Zoloft gained, on average, about a half-pound at six months and three pounds at two years.

In another 2018 study following participants for 10 years, people taking Zoloft had a slightly higher risk of gaining at least five percent of their body weight compared to those not taking an antidepressant. For someone weighing 160 pounds, that would be eight pounds or more of weight. But many people in the study did not experience weight gain.

“If weight gain occurs, it’s usually not significant,” says Kate Hanselman, PMHNP, vice president of clinical psychiatry at Thriveworks. “Sometimes it happens not because of a medication side effect, but because a person’s appetite returns as they start feeling better. That can reflect improved nutrition and recovery, rather than a problem with the medication itself.”

3 reasons Zoloft might affect body weight

No one knows for sure why Zoloft affects weight, but there are a number of ideas. Below, we’ll look at some of the most research-backed possibilities.

1. Restored appetite and eating patterns

Depression and anxiety often dull appetite, disrupt regular eating habits, and reduce pleasure in food. After starting on Zoloft and experiencing improvements in mental wellbeing, many people find their normal appetite and pleasure in food comes back. This shift can look like weight gain, even though it reflects recovery rather than a side effect of the medication.

Clinical experts have long noted that weight changes during antidepressant treatment may be in part due to a reversal of illness-related weight loss rather than a direct drug effect. Large observational studies support this interpretation, suggesting that weight gain tends to occur gradually after mood symptoms improve and varies widely between individuals.

In other words, as you start to feel better, your body may move back toward its previous weight baseline. This may be especially true if anxiety or depression were affecting your appetite.

“We often talk about weight changes as a possibility before starting the medication,” Hanselman explains. “Then we track weight over time alongside other changes, like appetite, habits, and symptoms. Looking at the full picture helps us understand what’s really driving the change.”

2. Changes in energy expenditure

Another possible explanation is that by easing anxiety and physical restlessness, antidepressants like Zoloft may subtly change how much energy your body uses each day.

Some people may get more energy and become more active after their mental health improves. For others, Zoloft may result in slightly less movement or lower energy expenditure without noticeable changes in eating. Over time, these small differences can add up to gradual weight gain.

3. Changes in serotonin levels

This is the most direct way Zoloft might affect weight, though researchers still don’t fully understand it.

Zoloft increases serotonin activity in the brain, and serotonin plays an important role in appetite regulation and satiety. In the short term, more serotonin is associated with reduced appetite, which may explain why some people experience mild weight loss when first starting an SSRI.

Over longer periods, some researchers have suggested that the brain may adapt to changes in serotonin levels in ways that influence appetite. Early on, increases in serotonin tend to reduce appetite. But over time, as your body adjusts to higher serotonin levels, its appetite-reducing effects may become weaker. When that happens, your appetite may return closer to its usual level.

How does weight gain on Zoloft compare to other SSRIs?

Providers don’t usually choose antidepressants based on weight effects alone. Other side effects and how well the medication works for you matter too. Still, below is a table that shows how Zoloft compares to other SSRIs in terms of weight gain, according to a 2024 study published in Annals of Internal Medicine.

Long-term weight gain with other SSRIs compared to Zoloft

Factors that raise risk of weight gain from Zoloft

If you’re living with other conditions that influence your weight, you may be more susceptible to weight changes after starting Zoloft. Here are a few examples:

Underlying metabolic conditions

Conditions such as hypothyroidism, insulin resistance, or polycystic ovary syndrome (PCOS) can affect how the body regulates weight. For people living with these conditions, small changes in appetite, activity level, or energy use may have a more noticeable impact on weight over time.

Ongoing sleep problems

Regardless of the reason, problems with sleep can influence appetite hormones and fullness cues. When sleep is inconsistent or less restorative, changes in hunger cues can make gradual weight gain more likely.

Emotional or stress-related eating patterns

For some people with depression or anxiety, eating patterns may become irregular during periods of high stress, low mood, or emotional distress. As symptoms improve with treatment, appetite often becomes more consistent. In some cases, this shift can lead to increased calorie intake and gradual weight gain, especially if eating had previously been suppressed or inconsistent.

For people with a current or past eating disorder, changes in mood and anxiety can also influence eating patterns in complex ways. When antidepressants are used, they’re typically just part of a broader treatment plan that also includes therapy and nutritional support. Weight changes during the course of treatment may reflect shifts toward more regular eating, rather than a worsening of symptoms.

Can Zoloft cause weight loss instead?

Yes, some people lose weight on Zoloft, especially during the early stages of treatment.

This usually happens when appetite temporarily decreases or when short-term digestive side effects, such as nausea or stomach upset, reduce appetite. In some cases, anxiety may briefly increase at the start of treatment, which can also reduce appetite. As your body adjusts, these effects typically ease, and weight often returns to your personal baseline over time.

“Early on, some people notice decreased appetite or mild stomach upset, which can lead to short-term weight loss,” Hanselman says. “These effects usually improve as the body adjusts, and weight often settles back toward a person’s usual baseline over time.”

When to talk to your provider—and what they can do

If you notice ongoing changes in your weight, appetite, or energy level while taking Zoloft, it’s worth bringing up with your provider. This is especially true if those changes feel uncomfortable or hard to manage. Small shifts are common early on, but persistent or accelerating changes are worth a closer look.

If they suspect it may be due to something other than Zoloft, they may check for other medical conditions. If it seems to be due to Zoloft, they may recommend adjusting your dosage. In some cases, they may recommend an alternative medication.

“I tell patients that weight gain is possible, but it’s not guaranteed,” Hanselman says. “We monitor weight during treatment, and if changes become bothersome, there are many options. That might include adjusting diet or activity, making medication changes, or getting additional support.”

The bottom line

Weight gain is possible with Zoloft, especially with long-term use. On average, Zoloft can result in about three pounds of weight gain after two years. But not everyone gains weight while taking Zoloft. If you have other medical conditions, ongoing sleep problems, or unhealthy eating patterns, you may be at higher risk of weight gain.

Frequently asked questions

Is weight gain on Zoloft permanent?

Weight gain from Zoloft isn’t always permanent, but it may not reverse on its own after stopping the medication. Some people gain weight when they first start the medication, while other people continue to gradually gain weight over a longer period of time. Speak with your provider if you’re concerned about weight gain after starting Zoloft.

How much weight gain is normal on Zoloft?

One study found an average weight gain of about a half of a pound (0.5 pounds) in the first six months, and 3 pounds over two years. But some people don’t gain any weight, while others lose weight. Poor sleep health, certain chronic conditions, and higher dosages may increase the risk for weight gain.

How long does it take for weight gain to show up on Zoloft?

Weight changes usually develop gradually over months rather than weeks. Appetite or sleep shifts may happen within the first few weeks, but noticeable weight changes typically appear after a few months, especially with higher doses or long-term use.

How do I know if the weight gain is from Zoloft or something else?

It may be difficult to know for sure. Stress, lifestyle changes, and other medical conditions can also affect weight. But tracking your appetite, sleep, mood, menstrual cycle, and movement habits can help you identify patterns. If weight changes started shortly after beginning Zoloft or increasing your dosage, it may be due to the medication.