Obese patients who lost weight while taking popular drugs such as Ozempic, Wigovy, Munjaro, and Zepbound had significantly reduced physical activity, according to study results presented Saturday at the Endocrine Society Annual Meeting ENDO 2026 in Chicago, Illinois.
This finding may come as a surprise, since many people think that losing excess weight will naturally make them more mobile. However, researchers found the opposite trend among people taking these drugs.
weight loss pills and muscle health
The drugs studied belong to a class known as glucagon-like peptide-1 (GLP-1) receptor agonists. This group includes semaglutide (Ozempic and Wegovy), tirzepatide (Mounjaro and Zepbound), liraglutide, and dulaglutide.
These drugs are very effective in weight loss, but they don’t just reduce body fat. It can also contribute to a loss of lean muscle mass, making physical activity especially important for maintaining strength and overall health.
Protecting your muscles is an important part of healthy weight loss, explained study leader Dr. Sajjana Maharjan of HSHS St. John’s Hospital in Springfield, Illinois.
Fitbit data showed decreased activity
To examine how activity levels changed after starting treatment, researchers analyzed data from the National Institutes of Health’s All of Us Research Program, which combines electronic health records and Fitbit activity data.
The study began with 1,950 obese adults who started GLP-1 treatment. Of these, 753 participants had sufficient wearable device data to be included in the final analysis. Most were female (78.6%), and the average age was 52.7 years.
Researchers compared physical activity before and after participants started taking the drug. They focused on daily steps and minutes of moderate-to-vigorous physical activity (MVPA).
Fewer steps and less exercise
The results showed a clear decrease in movement after the start of treatment.
The average number of steps taken per day decreased from 5,047 steps to 4,487 steps. Time spent in moderate-to-vigorous physical activity (MVPA) also decreased, from 28 to 22 minutes per day.
The biggest decreases were seen in men and people who reported joint or muscle pain. Findings did not vary by factors such as age, heart failure, or previous stroke.
Importantly, the researchers found no evidence that losing weight with these drugs made people more physically active.
You can’t put off exercising
“Many people think that weight loss naturally leads to increased physical activity, but our study suggests this is not the case. Our findings confirm that exercise is not optional for people taking these drugs. People need targeted interventions that promote physical activity alongside obesity medications,” Maharjan said.
According to the researchers, this is the first large-scale study to use data from wearable fitness trackers to investigate physical activity patterns in adults taking GLP-1 receptor agonists.
