People taking popular GLP-1 weight-loss drugs like Ozempic, Wegovy, Mounjaro, and Zepbound may be shedding pounds, but a new study suggests they are also moving less.
People with obesity who lost weight while taking popular medications such as Ozempic, Wegovy, Zepbound, and similar drugs became significantly less physically active, according to research presented at ENDO 2026, the Endocrine Society’s annual meeting in Chicago, Illinois.
The finding raises concerns because physical activity is important for preserving muscle mass and strength during weight loss. While these medications can help people shed excess pounds, exercise remains a key part of maintaining long-term health.
Weight Loss Drugs Can Reduce Muscle Along With Fat
Ozempic and Wegovy contain semaglutide, while Zepbound contains tirzepatide. These medications belong to a class of drugs known as glucagon-like peptide-1 (GLP-1) receptor agonists.
Although GLP-1 medications are highly effective for weight loss, they can reduce lean muscle mass as well as body fat. That makes regular physical activity especially important, according to study leader Sajana Maharjan, M.D., of HSHS St. John’s Hospital in Springfield, Illinois.
Fitbit Data Tracked Activity Before and After Treatment
To examine how activity levels changed after people started taking GLP-1 medications, researchers analyzed data from the National Institutes of Health’s All of Us Research Program. The program combines participants’ electronic health records with activity information collected from Fitbit wearable devices.
The study initially included 1,950 adults with obesity who began treatment with a GLP-1 medication. Of those, 753 had enough wearable-device data to be included in the analysis. Most participants were women (78.6%), and the average age was 52.7 years.
Researchers compared activity levels before and after treatment, focusing on daily step counts and minutes of moderate-to-vigorous physical activity (MVPA).
Daily Steps and Exercise Levels Fell
The results showed a clear decline in physical activity after participants started taking GLP-1 medications.
Average daily step counts dropped from 5,047 to 4,487. Time spent in moderate-to-vigorous physical activity (MVPA) also fell, decreasing from 28 minutes to 22 minutes per day.
The largest declines occurred among men and among people with joint or muscle pain. The findings remained consistent regardless of factors such as age, heart failure, or a previous stroke.
Researchers also found no evidence that losing weight with these medications led people to become more physically active.
Exercise Still Matters During GLP-1 Treatment
“While many assume that weight loss leads naturally to increased physical activity, our study suggests otherwise. The findings in our study reinforce that exercise cannot be optional for people taking these medications. People need targeted interventions that encourage physical activity alongside medication for obesity,” Maharjan said.
The researchers noted that this is the first large study to use wearable fitness tracker data to examine physical activity patterns among adults taking GLP-1 receptor agonists.
Meeting: ENDO 2026
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.