Weight Loss Drug Users Are Moving Less, Not More new Study Raises Alarm Over GLP-1 Exercise Habits

A new study is challenging one of the most widely held assumptions about GLP-1 weight loss drugs: that shedding pounds naturally motivates people to get up and move more. According to research presented at ENDO 2026, the Endocrine Society’s annual meeting in Chicago, the opposite may actually be happening.

The study, led by Dr. Sajana Maharjan and presented on June 14, drew on data from the National Institutes of Health’s All of Us Research Program a large-scale initiative that pairs participants’ electronic health records with their Fitbit wearable activity data. Researchers examined daily step counts for 753 adults living with obesity, tracking their movement both before and after they began taking a GLP-1 receptor agonist.

What they found was a clear and consistent dip in physical activity. On average, participants went from roughly 5,047 steps per day down to 4,487 a drop of about 560 steps. Time spent in moderate-to-vigorous physical activity also fell, sliding from 28 minutes a day to just 22. Perhaps most strikingly, the researchers found no evidence that weight loss from the medication translated into people becoming more active.

“While many assume that weight loss leads naturally to increased physical activity, our study suggests otherwise,” Maharjan said in a statement released by the Endocrine Society.

The declines were not uniform across all participants. Men and people dealing with joint or muscle pain saw the steepest drops in activity. Interestingly, other factors including age, a history of heart failure, or prior stroke did not meaningfully change the pattern, suggesting the trend holds across a fairly wide population. The average participant was 52.7 years old, and nearly 79 percent were women.

The researchers are calling the findings a first of their kind, describing it as the largest study to date using wearable fitness tracker data among adults on GLP-1 medications.

Outside experts who reviewed the findings say the results warrant attention, though they caution against drawing overly simple conclusions.

Dr. Hertzel Gerstein, a professor at McMaster University and a diabetes physician, noted that multiple factors could explain the activity decline, and that the drug itself may not be the sole or even primary cause. “People on these drugs should maintain and if possible, try to increase physical activity to maintain muscle mass and health,” he said in an emailed response. He added that this guidance applies broadly to anyone undergoing weight loss, since losing weight for any reason can lead to a reduction in muscle mass the body simply needs less muscle to carry around less weight.

Dr. Dana Small, a neurology and neuroscience professor at McGill University, was more pointed. She said GLP-1 drugs “are not a magic bullet,” and raised the possibility that some users may be mentally offloading the work of weight management onto the medication. “People may be thinking, ‘OK, the drug will do all the work, I don’t have to exercise’ it’s certainly a possibility and a likely contributor,” she said.

Small also flagged concerns about what happens when patients stop taking the drugs. Without continued exercise, she explained, the muscle mass that erodes during weight loss is rarely recovered. And when weight returns which it often does quickly once GLP-1 therapy ends it comes back mostly as fat rather than lean tissue, particularly for those who haven’t been staying active.

The findings arrive at a critical moment. GLP-1 drugs, once available only under brand names at steep prices, are becoming increasingly accessible. Generic versions have begun appearing on pharmacy shelves in Canada, and demand is expected to continue rising globally.

That growing reach makes the study’s message all the more urgent, according to Maharjan. “The findings reinforce that exercise cannot be optional for people taking these medications,” she said. “People need targeted interventions that encourage physical activity alongside medication for obesity.”

In other words, the drug may be doing its job but users still need to do theirs.