Before you plan a reunion with vaccinated friends or a trip to the office, you might want to try on those pants you haven’t worn in more than a year.

Many of us have eschewed pants during the pandemic lockdown, opting instead for the comfort of elastic waist shorts — or just underwear — as we navigate work from home attire.

If you’re finding out those pants don’t really fit anymore, you’re not alone.

In August, scientists in Denmark said rates of obesity may explode because of strategies to limit the spread of COVID-19. Although it’s not quite an explosion, researchers at the University of California, San Francisco, say we definitely gained weight during lockdown.

The initial shelter-in-place orders “coincided with an observed decrease in daily step counts,” the study authors wrote, “likely reflective of changes in physical activity and patterns of daily living, as well as concurrent self-reported increases in snacking and overeating.”

From February 1 to June 1, 2020, the researchers analyzed data on 269 participants in the Health eHeart Study. Volunteers in 37 states in Washington D.C. agreed to report weight measurements from their Bluetooth-connected smart scale. Many states were under shelter-in-place orders from March 19 to April 6 last year.

The researchers found participants gained about 1.5 pounds every month, regardless of geographic location. That comes to 18 pounds in a year.

“It is important to recognize the unintended health consequences SIP can have on a population level,” the study authors wrote. “The detrimental health outcomes suggested by these data demonstrate a need to identify concurrent strategies to mitigate weight gain, such as encouraging healthy diets and exploring ways to enhance physical activity.”

The study was published Monday in JAMA Network Open.