Chicago—Adults with obesity losing weight with glucagon-like peptide-1 (GLP-1) receptor agonist medications significantly decreased their physical activity, which is essential to protect muscle, according to a study being presented Saturday at ENDO 2026, the Endocrine Society's annual meeting in Chicago, Ill.
GLP-1 receptor agonists like semaglutide, liraglutide, dulaglutide and tirzepatide reduce not only fat but also lean muscle mass. This makes physical activity essential for preserving strength and long-term health, according to study lead Sajana Maharjan, M.D., of HSHS St. John's Hospital in Springfield, Ill.
The retrospective pre–post cohort study used data from the National Institutes of Health's All of Us Research Program, which links participants' electronic health records with their Fitbit activity data. Among the 1,950 adults with obesity who started a GLP-1 medication, researchers studied 753 people who had enough wearable-device data for analysis. The cohort was predominantly female (78.6%) with a mean age of 52.7 years.
Researchers compared each person's physical activity before and after starting treatment, focusing on daily step counts and moderate-to-vigorous physical activity (MVPA) minutes.
On average, daily steps decreased from 5,047 to 4,487 steps per day, and MVPA minutes fell from 28 to 22 per day after beginning a GLP-1 receptor agonist medication. The largest declines were seen in men and in people with joint or muscle pain, while factors such as age, heart failure or prior stroke did not change the results. The study found no evidence that weight loss from these medications led to increased physical activity.
"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.
This is the first large study analyzing data from wearable fitness trackers among adults taking GLP-1 receptor agonists.
