Millions of Americans are losing weight on GLP-1 drugs. A study presented June 14, 2026, at the Endocrine Society's ENDO 2026 meeting in Chicago has surfaced a concerning behavioral pattern: people on these medications are also moving significantly less.
Using Fitbit activity data linked to electronic health records from NIH's All of Us Research Program, the study found that adults with obesity who began GLP-1 therapy saw daily steps drop by 560 and moderate-to-vigorous physical activity (MVPA) decline by nearly 6 minutes per day — statistically significant changes that occurred alongside, not instead of, successful weight loss.
"GLP-1 receptor agonists are now used by millions of adults for weight loss, and we know from prior work that exercise is critical for preserving lean muscle and sustaining long-term weight reduction," said lead researcher Sajana Maharjan, M.D., of HSHS St. John's Hospital in Springfield, Illinois, in a statement to Healio. "What was missing was an objective answer to a basic question: Do patients actually become more active as they lose weight on these drugs?"
What the Study Found
Researchers identified 753 patients from NIH's All of Us Research Program with obesity who were prescribed a GLP-1 and had Fitbit data before and after their prescription. The cohort was 78.6% female, average age 52.7 years. Among these patients, 81.9% had musculoskeletal pain, 67.3% had hypertension, 48.1% had type 2 diabetes. GLP-1 drugs studied included semaglutide (Ozempic, Wegovy), liraglutide, dulaglutide, and tirzepatide.
According to Healio: mean daily steps declined from 5,047 to 4,487 (−560 steps; P < .001). Mean MVPA declined from 27.9 to 22.2 minutes (−5.7 min/day; P < .001). The decline was steepest among men and those with musculoskeletal pain.
| ENDO 2026 GLP-1 Physical Activity Study | Data |
| Study presented | ENDO 2026, Chicago, June 14, 2026 |
| Lead author | Sajana Maharjan, M.D., HSHS St. John's Hospital, Springfield, IL |
| Data source | NIH All of Us Research Program (Fitbit + EHR linkage) |
| Participants | 753 adults with obesity |
| Average age | 52.7 years (78.6% female) |
| With musculoskeletal pain | 81.9% |
| Average daily step decline | 5,047 → 4,487 (−560; P < .001) |
| Average MVPA decline | 27.9 → 22.2 min/day (−5.7 min; P < .001) |
| Steepest decline | Males; those with musculoskeletal pain |
| Status | Conference presentation — not yet peer-reviewed published |
Why This Matters — The Muscle Loss Problem
GLP-1 drugs reduce body fat — but also lean muscle mass. Research estimates 20–40% of GLP-1 weight loss comes from lean tissue. Physical activity, especially resistance training, is the primary tool for preserving muscle during caloric restriction. When patients simultaneously reduce calories (via GLP-1 appetite suppression) and reduce exercise, the combination risks loss of muscle mass, bone density, and functional strength — even as the scale improves.
According to Neuroscience News coverage of the ENDO 2026 finding: "Doctors cannot simply assume their patients will start working out once they lose weight. Medical providers must treat structured exercise as a non-negotiable part of the prescription."
"This study aligns with my clinical experience," said Dr. Mir Ali of MemorialCare Surgical Weight Loss Center, commenting to Healthline. "I often find that patients feel more fatigued while losing weight, which can make exercise feel like a chore. But it's important for patients to continue regular exercise. The whole goal is to improve health and increase longevity."
For patients on GLP-1 drugs: weight loss is real but incomplete as a health intervention. Resistance training — not just aerobic activity — should be non-negotiable from day one of therapy. Clinicians should incorporate exercise prescriptions, preferably including at least two resistance sessions per week, into GLP-1 management protocols.
Frequently Asked Questions
What did the ENDO 2026 GLP-1 exercise study find?
753 adults with obesity using Fitbit wearables saw daily steps drop 560 and MVPA decline 5.7 minutes/day after starting GLP-1 medications — despite successful weight loss.
Why is reduced physical activity a problem for GLP-1 users?
GLP-1 drugs reduce both fat mass and lean muscle mass. Physical activity — especially resistance training — is the primary defense against muscle loss during weight reduction. Combined caloric restriction and activity reduction accelerates lean mass loss.
Are these findings definitive?
No. This was a conference presentation at ENDO 2026, not yet peer-reviewed published. Preliminary findings, but consistent with clinical experience.
What should GLP-1 users do?
Integrate resistance training from day one — at least 2 sessions per week of strength-based exercise, combined with walking. Discuss an exercise plan with your prescribing physician.
Who was most affected in the study?
Men and those with musculoskeletal pain showed the steepest physical activity decline.
