GLP-1 Medications and Muscle Mass: What Patients Should Know

Weight loss on GLP-1 medications comes from both fat and lean mass, and across trials roughly one-quarter to two-fifths of the weight lost is lean tissue. That is why a 2025 joint advisory from four major medical societies puts muscle preservation at the center of obesity treatment rather than treating it as an afterthought. At Zest Regen Health in Columbia, Maryland, GLP-1 support is built into a supervised weight loss program with evaluation, testing, nutrition guidance, and follow-up.

What the body-composition research shows

In the STEP 1 trial of semaglutide, a DEXA body-scan substudy found that over 68 weeks total fat mass fell by about 19% while total lean body mass fell by about 10% in participants on the highest dose. Analyses of tirzepatide trials similarly show roughly one-quarter of weight lost coming from lean mass. Fat loss still dominates, and the proportion of fat to lean lost improves with greater overall weight loss, but the lean loss is real and worth planning for.

Why lean mass matters

• Muscle supports strength, balance, and everyday function
• Lean mass is metabolically active and contributes to resting energy use
• Lean loss can be more noticeable in older adults or people starting with less muscle
• Weight regain tends to come back as fat, so protecting muscle on the way down supports long-term body composition

What the 2025 joint advisory recommends

In May 2025, the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society published a joint advisory in the American Journal of Clinical Nutrition on nutritional priorities during GLP-1 therapy. Its three pillars are adequate protein, structured resistance training, and nutrition assessment with professional support.

• Protein at roughly 1.2 to 1.6 grams per kilogram of body weight per day, spread across meals
• Structured resistance training combined with aerobic activity, typically two or more strength sessions per week plus regular moderate aerobic exercise
• Baseline nutrition assessment, with referral to a registered dietitian or exercise professional where appropriate

How a supervised program builds this in

Muscle preservation should be part of the treatment plan, not a separate conversation. At Zest Regen Health, a medical weight loss program starts with an evaluation and baseline testing, includes nutrition and activity guidance alongside medication when medication is appropriate, and uses scheduled follow-up to review labs, dosing, and progress over time.

See the GLP-1 weight loss program at Zest Regen Health

Read how the full medical weight loss program is structured at the Columbia clinic

Understand what happens after stopping a GLP-1 medication

Explore weight management as a condition we evaluate

Meet our physicians, who guide evaluation and follow-up at the Columbia clinic

Weight loss programs in Columbia, Maryland

Zest Regen Health is located at 8860 Columbia 100 Parkway, Suite 216, Columbia, MD 21045, serving Columbia, Howard County, Ellicott City, Clarksville, and surrounding communities within roughly 20 miles. Call (443) 917-6500 to ask about GLP-1 programs, or book a consultation to discuss your weight history, your labs, and what a supervised program would include.

Next step

If you are considering a GLP-1 program, ask what happens beyond the prescription: testing, nutrition guidance, exercise support, and follow-up. Book a free 15-minute consultation at the Columbia clinic and our team will explain how a supervised program is structured and what your plan would include.