If You've Gained Weight Recently, This OTC Medication May Be to Blame

This common medication can have profound effects on your waistline.

If you've recently packed on a few pounds, you're hardly alone. A March report published by the American Psychological Association (APA) on the stresses of the pandemic found that 42 percent of Americans have experienced undesired weight gain since COVID first hit. But before you dismiss your weight gain as the result of pandemic stress alone, you should first consider when you started gaining. If it began as recently as the spring—and if you take one particular type of medication that people commonly take during this season—your expanding waistline may be the result of a surprising side effect. Read on to find out what common OTC medication is triggering your spring weight gain, and for more must-have info about your OTC meds, This Is When You Should Take Tylenol Instead of Advil, Doctors Say.

Antihistamines can trigger weight gain.

woman allergies spring

According to a study from the Yale University School of Medicine, antihistamines—commonly used to treat spring allergies—are known to cause significant weight gain. The researchers reviewed medical data from 268 adults (174 female and 94 male) who reported the use of antihistamines and compared that data with that from 599 people (401 female and 198 male) who did not.

They found that those who regularly used antihistamines "displayed significantly greater BMI, waist circumference, and insulin levels," suggesting "a correlation between using antihistamines and a higher weight." They determined that men who used antihistamines weighed an average of 22 pounds more than those who did not, while women who used the medication weighed an average of 10 pounds more than their non-medicated counterparts. And for more health news sent right to your inbox, sign up for our daily newsletter.

These brands have the greatest impact on your weight.

Sam's Club pharmacy

The Yale study specifically looked at two types of antihistamines which, at the time of the study, were only available by prescription: Zyrtec and Allegra. Today, these brands are available as OTC allergy treatments alongside Benadryl—and the Obesity Medicine Association reports that because they "have the same strength as the prescription versions," they most likely trigger the same side effects. And for more on essential medical news, If You Take This Medication, U.S. Officials Have a New Warning for You.

They increase appetite and decrease energy.

Young woman eating ice cream near refrigerator at night
DrGrounds / iStock

"From clinical experience and solid scientific research demonstrating how histamine affects our appetites, it is safe to say that antihistamines probably do affect weight gain," writes Vivek Gupta, MD, MPH, a weight loss specialist, via the Obesity Medicine Association site. He explains that histamines decrease hunger by "affecting the appetite control center in our brains." Antihistamines, on the other hand, interfere with the signals that tell us when we're full, resulting in overeating.

Gupta also notes that antihistamine medications can make users feel sluggish, leading to a reduction in the number of calories they burn over the course of the day. "While first generation antihistamines like Benadryl are more prone to make you sleepy, even second-generation medications like Zyrtec, when broken down by the body, result in byproducts that have a mild sedative effect," Gupta explains.

One brand may have a less pronounced effect on your weight.

A person holding pills and a nasal inhaler at the pharmacy

If you've experienced unexpected weight gain and you take any of these types of antihistamines, Gupta suggests switching to a different formulation.

"If you need an antihistamine for frequent allergy symptoms…the best choice is Claritin because it does not cross into the brain and has less effect on appetite and sedation," he says. "Otherwise, steroid nasal sprays, decongestants, and just reducing exposures to allergens are other options," the weight loss specialist concludes. And for more on the side effects of your OTC routine, If You Can't Sleep, This OTC Medication Could Be Why, Experts Say.

Lauren Gray
Lauren Gray is a New York-based writer, editor, and consultant. Read more
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