GLP-1 drugs like semaglutide (the active ingredient in Ozempic and Wegovy) have changed weight loss treatment for the better. That said, people taking these medications might be less inclined to keep up with other healthy habits, research out today shows.
Doctors at HSHS Saint John’s Hospital in Illinois and others examined Fitbit data from people with obesity who were prescribed a GLP-1 medication. People’s level of physical activity significantly decreased after starting a GLP-1, they found. Though preliminary, the study’s findings suggest that promoting exercise should be an important part of managing the care of patients who go on these drugs, the researchers say.
The GLP-1 paradox
While exercise isn’t a major driver of weight loss, at least for most people, it’s long been recommended alongside diet. When people lose weight, they lose both fat and lean body mass, some of which can include muscle. Exercise can help stave off this muscle loss and maintain people’s physical strength and functioning.
Though people can lose weight through lifestyle changes alone, the addition of GLP-1 therapy has proven to be much more effective on average. The researchers wanted to understand how people taking these drugs might alter their level of exercise, so they turned to data from the All of Us research program, an ongoing project that tracks the health of a large, diverse group of Americans.
They focused on a subset of volunteers, 753 in total, who were prescribed a GLP-1 for their obesity and also had Fitbit activity data available before and after their prescription. These GLP-1s included the newest drugs on the market, like semaglutide and tirzepatide, as well as older medications liraglutide and dulaglutide.
Overall, people’s physical activity decreased after starting a GLP-1, the researchers found. The average daily steps of GLP-1 users dropped from 5,047 to 4,487, for instance, while their daily level of moderate-to-vigorous activity lowered from 28 minutes to 22 minutes. This decline in exercise was steeper among men as well as people who also reported having some amount of musculoskeletal pain.
What to do
The team’s research is set to be presented this weekend at ENDO 2026, the Endocrine Society’s annual meeting. That means these findings are preliminary, so they should be viewed with more caution than usual. Other research, including from large-scale clinical trials, has also indicated that muscle loss isn’t a major concern for people taking a GLP-1 and that people’s physical functioning generally improves while on these drugs.
Still, there are some GLP-1 users who are at greater risk of muscle loss than others, particularly older people. And since exercise is one of the healthiest things you can do no matter your current weight or medication status, it should still be concerning if many GLP-1 users are dropping their gym or walking routine. The researchers argue that people going on these drugs should be reminded about the importance of maintaining their exercise habits.
“These findings suggest that weight loss alone may not promote increased physical activity, highlighting the need for targeted interventions that encourage physical activity alongside pharmacologic therapy,” they wrote in their paper.
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