Adults with obesity who began taking GLP-1 receptor agonist medications showed declines in Fitbit-measured physical activity after starting treatment, according to a retrospective study presented Saturday at ENDO 2026, the Endocrine Society’s annual meeting in Chicago.
Researchers analyzed data from the National Institutes of Health’s All of Us Research Program, which links participants’ electronic health records with Fitbit activity data.
The retrospective pre–post cohort study identified 1,950 adults with obesity who started a GLP-1 medication, and focused its activity analysis on 753 participants who had sufficient wearable-device data. The cohort was predominantly female (78.6%), with a mean age of 52.7 years.
After participants began GLP-1 receptor agonist treatment, average daily steps decreased from 5,047 to 4,487 steps per day. Minutes of moderate-to-vigorous physical activity also fell, from 28 minutes per day to 22 minutes per day.
The largest declines were reported among men and among participants who reported joint or muscle pain. By contrast, factors including age, heart failure, or prior stroke did not change the results.
Study lead Sajana Maharjan, M.D., of HSHS St. John’s Hospital in Springfield, Illinois, said the findings suggest weight loss does not necessarily translate into more movement.
“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 described the analysis as the first large study to examine wearable fitness tracker data among adults taking GLP-1 receptor agonists. The Endocrine Society also noted that GLP-1 receptor agonists can reduce both fat and lean muscle mass, underscoring the importance of physical activity to help preserve strength and long-term health.
