Obese adults who lost weight with glucagon-like peptide-1 (GLP-1) receptor agonist drugs significantly reduced physical activity, which is essential to protect muscles, according to study results presented Saturday at the Endocrine Society Annual Meeting ENDO 2026 in Chicago, Illinois.
GLP-1 receptor agonists, such as semaglutide, liraglutide, dulaglutide, and tirzepatide, reduce not only fat but also lean muscle mass. That’s why physical activity is essential to maintaining strength and long-term health, says lead researcher Sajjana Maharjan, MD, of HSHS St. John’s Hospital in Springfield, Illinois.
This 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 and Fitbit activity data. Out of 1,950 people Researchers surveyed 753 obese adults who had started GLP-1 treatment and had sufficient wearable device data for analysis. This 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 steps and minutes of moderate-to-vigorous physical activity (MVPA).
On average, after starting GLP-1 receptor agonist administration, daily step count decreased from 5,047 steps per day to 4,487 steps per day, and MVPA minutes decreased from 28 to 22 minutes per day. The greatest reductions were seen in men and people with joint or muscle pain, but the results were not altered by factors such as age, heart failure, or history of stroke. The study found no evidence that weight loss with these drugs led to increased physical activity.
Many people think that weight loss naturally leads to increased physical activity, but our research suggests this is not the case. Our findings confirm that exercise is not optional for people taking these medications. People need targeted interventions that promote physical activity alongside obesity medications. ”
says Dr. Sajjana Maharjan of HSHS St. John’s Hospital in Springfield, Illinois.
This is the first large-scale study to analyze data from wearable fitness trackers in adults taking GLP-1 receptor agonists.
