GLP-1 Users Move Less, Lose More Muscle — Why Strength Training Is No Longer Optional

There’s a quiet assumption many patients bring to a GLP-1 prescription: the weight comes off, the body gets lighter, and movement gets easier. Wearable data presented at ENDO 2026 on June 13 says the opposite.

Adults with obesity who started a GLP-1 receptor agonist became measurably less active after beginning treatment. Daily steps fell from 5,047 to 4,487. Moderate-to-vigorous activity dropped from 28 to 22 minutes per day. The study used linked Fitbit data on 753 adults from the NIH All of Us Research Program — the first large study to use wearable tracker data rather than self-reports — and found no evidence that weight loss translated into moving more.

Biggest declines were in men and in people with joint or muscle pain. Lead author Dr. Sajana Maharjan: “Exercise cannot be optional for people taking these medications.”

Why Movement Matters More Than the Scale

GLP-1 medications don’t only shrink fat. They reduce lean muscle mass too. If you’re simultaneously becoming less active, you’ve stacked two effects — appetite down, intake down, and so is the stimulus that tells your body to hold onto muscle. The result: “lighter but weaker.”

The Colorado Lens

Chad Harris, Ph.D., chair of Exercise and Sport Sciences at Metropolitan State University of Denver, made the same point: “If we’re not effectively training and exercising along with those GLP-1s, we can lose muscle mass, too.” His colleague Philip Skaff adds that without addressing stress, sleep, and nutrition, “they are not addressing the root cause.”

What “Doing It Right” Looks Like

• Two to three resistance sessions a week. Not cardio — resistance. Mechanical load is the muscle-retention stimulus.
• Protein at ~1.6 g per kilogram of body weight per day, spread across meals.
• Schedule activity deliberately. It does not happen by accident on these medications.
• Track body composition, not just the scale. Losing 30 pounds of fat and 5 of muscle is a very different year than losing 20 of fat and 15 of muscle.

The Honest Caveat

One retrospective study, and the decline is an average — plenty of patients maintain or increase exercise. The take-home isn’t “GLP-1s make you sedentary.” It’s that the medication does not protect activity, and without a plan, the average patient trends the wrong direction.

Bottom Line

A GLP-1 prescription reduces the work of eating. It does not reduce the work of preserving the body you want at the end. The Maharjan data — the first of its kind — makes that point with numbers.

Your job: pair the medication with structured resistance training and adequate protein. Your doctor’s job: tell you that, and mean it.

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Dr. Ethan Lazarus, MD, MFOMA, Dipl. ABOM
Clinical Nutrition Center
5995 Greenwood Plaza Blvd, Suite 150, Greenwood Village, CO 80111
(303) 750-9454 | clinicalnutritioncenter.com