8 Common Medications That Can Cause Weight Gain

“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 — including prednisone and methylprednisolone — are prescribed for everything from severe allergies and rashes to rheumatoid arthritis, but they come with 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. 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, the chance of chronic migraine is three to five 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. 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,” Umashanker says. “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, according to 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 as topiramate (Topamax) or zonisamide (Zonegran), both of which are also prescribed for migraines and associated with weight loss.

8. Antipsychotics

People with mental health disorders are two to three times more likely to have obesity (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 of those drugs cause weight gain. Over the course of treatment, around 7 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), Batsis says.

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 newer medications on the market. “They tend to have lower risk of weight gain,” Batsis says. Keep in mind that everybody is different, he hastens to add. “While we can generalize, these medications may affect different individuals in different ways.”

Why do some medications cause weight gain?

​​The source of what causes weight gain varies between medications. Some may increase your appetite, tempting you to eat more, resulting in a few pounds creeping on. Others might slow your metabolism down so calories aren’t burned as quickly. Certain classes of drugs may make your body retain water. Although this wouldn’t mean you’ve put on extra fat, it will make you weigh more when you hit the scale. In other instances, the way your body stores and absorbs sugar and other nutrients may be affected, according to the University of Rochester.

Symptoms of medicine-related weight gain

The biggest symptom of medicine-related weight gain is staring up at you from the scale: You weigh more than you normally do. Apart from the weight gain, you may notice additional symptoms such as water retention, a change in appetite (you’re hungry all the time) or maybe more difficulty in exercising. How do you know a particular medication is to blame?

Clinical guidelines categorize medications as those that promote weight loss, weight gain or have weight-neutral effects, but inconsistencies exist.

Defining the effects of medication on weight isn’t an exact science. When prescribing medications that have the potential to cause weight gain, doctors “should provide patients information on the potential side effects and ideally have an ability to monitor accordingly,” Batsis says. “Careful evaluation of weight during office visits, or self-monitoring, is critically important. [Doctors] really need to take a [medical] history and carefully discuss with the patient whether there are other conditions at play."

What to do if medications cause 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 (such as brisk walking) and strength training. “Countering medication-induced weight loss is difficult,” Batsis says. “Trying to engage individuals in health promotion efforts is key.” 

Although 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.”