A major new study presented at the Endocrine Society annual meeting (ENDO 2026) in Chicago, Illinois, has revealed a troubling trend among users of popular GLP-1 weight-loss medications. According to the research, people with obesity who take drugs such as semaglutide (sold as Ozempic and Wegovy) and tirzepatide (sold as Mounjaro and Zepbound) became significantly less physically active after starting treatment.
The findings showed that average daily step counts among participants fell from 5,047 to just 4,487 steps per day — a meaningful decline that raised alarm bells among endocrinologists and public health experts. Time spent in moderate-to-vigorous physical activity also dropped sharply, from 28 minutes to only 22 minutes per day. These reductions suggest that users may be relying too heavily on the medications alone to manage their weight.
Researchers noted that the greatest decline in physical activity was observed among males and people who also suffered from musculoskeletal pain. This subgroup appeared particularly vulnerable to becoming sedentary after beginning GLP-1 therapy, possibly because the initial weight loss reduced their motivation to exercise or because joint discomfort limited movement even as body weight decreased.
One of the most pressing concerns highlighted by the study is the impact on muscle mass. GLP-1 receptor agonists are known to reduce not only fat but also lean muscle tissue. When combined with a decrease in physical activity, this dual effect could lead to significant loss of strength, reduced metabolic rate, and increased frailty — outcomes that undermine the overall health benefits of weight loss.
Millions of people worldwide now take these blockbuster medications, which have transformed the landscape of obesity treatment. However, the study underscored that long-term weight management is most effective when pharmaceutical intervention is paired with consistent exercise. Without regular physical activity, patients risk losing the muscle and cardiovascular fitness needed for sustained health improvements.
The researchers urged clinicians who prescribe GLP-1 drugs to actively monitor their patients' physical activity levels and encourage structured exercise programs alongside medication. They emphasized that simply losing weight on the scale does not equate to improved overall fitness, and that preserving lean muscle mass through resistance training and aerobic activity remains essential for long-term well-being.
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