That paradox was a major talking point at the Endocrine Society’s annual meeting (ENDO 2026).
The study, titled “Losing Pounds, Not Gaining Steps: The Paradox of GLP-1 Receptor Agonist Therapy,” was led by Dr. Sajana Maharjan from HSHS St. John’s Hospital. It challenged the common assumption that losing weight naturally motivates people to move more.

📊 Study Overview & Methodology

The research was a retrospective pre-post cohort study that utilized real-world data from the National Institutes of Health’s All of Us Research Program. Crucially, instead of relying on self-reported surveys, the researchers linked patients’ electronic health records directly with their objective Fitbit wearable data.

• Participants: 753 adults with obesity who initiated GLP-1 receptor agonist therapy (such as semaglutide or tirzepatide) and had sufficient tracker data.
• Demographics: Mean age of 52.7 years; 78.6% female.

📉 Key Findings: The Exercise Deficit

The data revealed a statistically significant decline in physical output across the board after patients started taking GLP-1 medications: Activity Metric Before GLP-1s After GLP-1s Average Decline Daily Step Count 5,047 steps/day 4,487 steps/day -560 steps (p < 0.001) Moderate-to-Vigorous Physical Activity (MVPA) 27.9 mins/day 22.2 mins/day -5.7 minutes (p < 0.001)

🔍 High-Risk Subgroups

While factors like age, morbid obesity, or a history of cardiovascular events did not alter the general downward trend, two groups experienced significantly steeper declines:

• Men: Experienced a much sharper drop in both daily steps (-986 vs. -445 for women) and MVPA (-15.3 mins vs. -2.9 mins for women).
• Patients with Musculoskeletal (MSK) Pain: Those dealing with pre-existing joint or muscle pain saw their steps drop by an average of 679 steps, compared to a negligible change of just 22 steps for those without pain.

💡 Why This Matters

GLP-1 medications cause rapid weight loss, but that loss consists of both body fat and lean muscle mass. Physical activity—specifically resistance and weight-bearing exercise—is necessary to protect muscle tissue, maintain functional strength, and prevent metabolic slowdown.

The Takeaway: The study authors emphasized that clinicians cannot treat exercise as an optional “add-on” or assume patients will spontaneously become more active as they lose weight. Instead, structured exercise counseling and target support need to be co-prescribed alongside GLP-1 therapy from day one.