8 Common Medications That Can Cause Weight Gain

2. Antidepressants

If you’ve been on an antidepressant for a while now and you’ve put on weight, it could be a sign of improved mood if weight loss was a symptom of your depression.

Significant weight gain, on the other hand, is likely a side effect of the medication itself, especially if you’re taking an SSRI (short for selective serotonin uptake inhibitor), the most commonly prescribed class of antidepressants. Here’s why: SSRIs, such as paroxetine (Paxil), sertraline (Zoloft) and citalopram (Celexa), work by “increasing the amount of serotonin in your brain, which is a key neurotransmitter involved in depression,” Batsis says. “Serotonin, though, is also implicated in the biological and neurotransmitter processes that regulate weight and appetite. There are many serotonin receptors, but at a high level they interfere with this process.”  

The good news? With many of the newer second-generation antidepressants, there is often no weight gain; some, such as bupropion (Wellbutrin), may even result in weight loss, Batsis says, echoing the results of research published in 2018 in the journal Diabetes, Metabolic Syndrome and Obesity.

“Bupropion is less likely to cause weight gain and when coupled with naltrexone (Vivitrol) is a potential treatment for obesity,” he says. “Yet in older adults, bupropion, while safe, needs to be counterbalanced with other medical issues as it may have more central nervous system side effects.” His advice: Work with your medical team to find the best treatment for your situation.  

3. Beta-blockers

Beta-blockers work by slowing the heart rate, the heart’s workload and its output of blood, all of which lowers blood pressure. That’s why they’re often prescribed as a treatment for hypertension, angina and irregular heartbeat. If you’re on a beta-blocker, no one has to tell you the side effects include fatigue, insomnia and a slow heartbeat. All of those can add up to a less physically active lifestyle, which — no surprise — may result in extra weight.

“Weight gain often occurs in the first few months after initiating beta-blockers like atenolol or metoprolol,” Batsis says. That’s “thought to be due to changes in metabolism, insulin sensitivity and impact on skeletal muscle metabolism.”

If you’re on a beta-blocker and weight gain is an issue, talk to your doctor about possible alternatives such as carvedilol, a nonspecific beta-blocker; angiotensin converting enzyme (ACE) inhibitors; angiotensin receptor blockers (ARBs); or calcium blockers, Batsis says.  

4. Oral corticosteroids

Oral corticosteroids — like prednisone and methylprednisolone — are prescribed for everything from severe allergies and rashes to rheumatoid arthritis, but they come with a number of side effects — among them, weight gain. The culprit? Fluid retention.

“Electrolyte imbalances lead to water retention,” Umashanker explains. “Oral steroids also reduce the body’s sensitivity to insulin, leading to insulin resistance.” That, in turn, ramps up production of the hunger hormone ghrelin, which stimulates appetite.

To avoid weight gain, Umashanker recommends a diet rich in low-glycemic foods such as fruits and vegetables, beans, minimally processed grains, low-fat dairy and nuts, all of which are “slowly digested and absorbed, causing a slower and smaller rise in blood sugar levels.”

5. Migraine meds

Talk about a vicious cycle: If you’re overweight and suffer from migraines, the extra weight puts you at greater risk for more frequent and more severe migraines. And yet weight gain is a side effect of some migraine-preventive meds, including propranolol (Inderal) and divalproex sodium (Depakote).

According to the American Migraine Foundation, people at a healthy weight who experience migraines have about a 3 percent chance of developing chronic headaches. For people who are overweight and for people with obesity, however, the chance of chronic migraine is 3 to 5 times greater. 

If you’re on a migraine-preventive medication that’s causing weight gain, talk to your doctor about switching to one that has the potential to suppress appetite, such as topiramate (Topamax), zonisamide (Zonegran) or protriptyline (Vivactil).

6. Antihistamines

It’s easy to assume that over-the-counter meds don’t carry serious side effects because they’re so readily available. But just because something is available without a prescription doesn’t mean it’s risk free. For instance, research suggests that taking an antihistamine on a regular basis—to treat allergies, for instance—can result in weight gain. In fact, cyproheptadine (Periactin) has been used specifically as an appetite stimulant to help people gain weight. Other  antihistamines associated with weight gain include cetirizine (Zyrtec), fexofenadine (Allegra), and desloratadine (Clarinex).

“The major study which demonstrates the relationship between antihistamines and weight gain comes from the journal Obesity,” says  Umashanker. “It revealed that men who used antihistamines had an average weight of 214 pounds versus 192 for those not on antihistamines and women had an average weight of 176 pounds on antihistamines versus 166 pounds for those not on antihistamine.”

Why? Histamine, a chemical in the body known to be a key player in allergic responses, decreases hunger by affecting the appetite control center in the brain, so it makes sense that an antihistamine would have the opposite effect, interfering with the “I’m full” signal coming from the rest of the body, notes The Obesity Medicine Association. 

7. Anti-epilepsy drugs

​​A review of research published in Epilepsia suggests that people with epilepsy—a brain disorder that causes seizures —exercised less and tended to be obese even if their seizures were under control. Conventional wisdom suggests that a fear of doing anything that could provoke a seizure would figure into why people with epilepsy are less inclined to be physically active. But anti-epilepsy drugs have been shown to play a significant role: valproic acid (Depakene), gabapentin (Neurontin), pregabalin (Lyrica), and possibly carbamazepine (Carbatrol) are all associated with weight gain. 

If you’re taking any of these and experiencing weight gain, talk to your doctor about possible alternatives such topiramate (Topamax) or zonisamide (Zonegran), both of which are also prescribed for migraines and are associated with weight loss.

8. Antipsychotics

People with mental health disorders are two to three times more likely to be obese (meaning a body mass index, or BMI, of 30 or more) than the general population. A review of research examining antipsychotic medicine explains why: most cause weight gain. Over the course of treatment, around seven in 10 patients will gain weight, rapidly in the initial period after starting these meds, but it continues over the long term. The risk appears to be highest with olanzapine (Zyprexa) and clozapine (Clozaril), says Batsis.

Making matters worse, these types of drugs impair glucose function and increase cholesterol and triglycerides, putting patients more at risk for developing metabolic syndrome, according to a review of research in Neuropsychiatric Disease and Treatment.

If you’re taking an antipsychotic for bipolar disorder, schizophrenia, or depression and you’re experiencing weight gain talk to your doctor about some of the newer medications on the market. “They tend to have lower risk of weight gain,” says Batsis. Keep in mind, though, that everybody is different, he hastens to add. “While we can generalize, these medications may affect different individuals in different ways.”

How can you treat medication-related weight gain?

If switching meds isn’t an option, that doesn’t mean you’re powerless over the extra pounds. Consider meeting with a registered dietitian who can help you learn how to make healthier food choices.

Getting more exercise can also help treat weight gain, especially a combination of cardio (like brisk walking) and strength training. “Countering medication-induced weight loss is difficult,” says Batsis. “Trying to engage individuals in health promotion efforts is key.” 

And while it may be tempting to turn to an anti-obesity drug to lose the unwanted pounds, Batsis recommends against doing so. “Treating side effects of one medication with another can be problematic and lead to what we term polypharmacy,” he says. “That, in and of itself, can lead to adverse events.”

Editor’s note: This story, originally published Feb. 18, 2022, has been updated to include new information.