Updated October 18, 2026 · By the DEXASCAN.COM Team
Quick answer: Yes, GLP-1 medications can cause muscle loss. 2026 research found that about 31–35% of the weight lost on drugs like semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) can come from lean mass, versus about 14–21% with diet and exercise alone. The only way to know how much you are losing is to measure it, and a DEXA scan is the gold standard for that.
Key takeaways
- Two 2026 reviews put lean-mass loss on GLP-1s at roughly one-third of total weight lost.
- Resistance training and enough protein are the best-supported ways to protect muscle.
- A baseline DEXA scan, then a rescan every 8–12 weeks, shows whether you are losing fat or muscle.
- DEXA, VO2 Max and RMR testing start at $89 on DEXASCAN.COM.
If you're losing weight on Ozempic, Wegovy, Mounjaro or Zepbound, the number on your bathroom scale is only half the story. Two major pieces of research released in 2026 put a number on something many people on GLP-1 medications have suspected: a meaningful share of the weight that comes off can be lean mass, not just fat. Here's what the new studies found, why it matters, and how a DEXA scan shows you exactly what your body is losing.
Do GLP-1 medications cause muscle loss? What the 2026 research found
The Annals of Internal Medicine review. In April 2026, researchers led by Dr. John Batsis at the University of North Carolina published a systematic review of 36 randomized controlled trials of semaglutide, tirzepatide, dulaglutide and liraglutide. Across those trials, the median share of total weight lost that came from muscle-based measures was about 35%, and roughly two-thirds of the studies exceeded the commonly used 25% benchmark for lean-mass loss during weight loss.
The European Congress on Obesity data. In May 2026, a meta-analysis of 21 randomized trials presented at the European Congress on Obesity found that fat-free mass made up about 31.5% of weight lost on incretin drugs, compared with roughly 14–21% with diet and exercise. That put GLP-1 medications close to bariatric surgery (about 33%) for the share of lean mass lost.
There's encouraging news too. A separate analysis of 486 patients presented at the same meeting found that fat still made up 80–85% of the weight lost, and relative muscle mass was preserved or even improved in over 70% of patients. The difference? Those patients were counseled on exercise as part of their care.
Why does muscle loss on Ozempic or Mounjaro matter?
The researchers were clear on one point: success shouldn't be judged by weight lost alone. Lean muscle drives your metabolism, protects your joints and bones, keeps blood sugar in check and is one of the strongest predictors of healthy aging (learn about ALMI, the DEXA number that predicts how well you’ll age). Losing too much of it can mean:
- A slower resting metabolism, which makes weight regain more likely when you stop the medication (see RMR and metabolic adaptation)
- Less strength and stamina in everyday life
- Lower bone density over time, especially after 40
- Looking "smaller" but not leaner or more toned
The study authors also cautioned that percentages can mislead. What matters is how much muscle you lose compared with your own starting point. That's impossible to know without measuring it.
How do you know if you're losing fat or muscle?
A DEXA (dual-energy X-ray absorptiometry) scan is the gold standard for body composition. In about 10 minutes, it measures:
- Fat mass and body fat %, including where you carry it
- Lean muscle mass in your arms, legs and trunk
- Visceral fat, the dangerous fat around your organs
- Bone density
New to DEXA reports? Here’s how to read your DEXA scan report, every number explained.
Because DEXA separates fat from lean tissue region by region, it answers the question every GLP-1 patient should be asking: "Am I losing fat, or am I losing muscle?"
How to protect muscle on a GLP-1: a simple plan
- Get a baseline DEXA scan before you start, or as early in treatment as possible. (Why it matters: DEXA scans for GLP-1 users.)
- Lift something. The research consistently points to resistance training, 2–3 sessions a week, as the best way to protect lean mass.
- Prioritize protein at every meal, even when your appetite is low. Ask your provider or dietitian for a target that fits you.
- Rescan every 8–12 weeks at the same location so your results are directly comparable (how often should you get a DEXA scan?).
- Bring your results to your prescriber. If lean mass is dropping fast, your dose, nutrition or training plan may need adjusting.
Want to see your metabolism, too? Add an RMR (resting metabolic rate) test to find out how many calories you actually burn at rest, so you can fuel your body without guessing. Here’s why your calorie calculator is wrong and how RMR fixes it, and how DEXA, RMR and VO2 Max work together.
Frequently asked questions
Does Ozempic or Wegovy cause muscle loss?
It can. Semaglutide causes weight loss from both fat and lean mass. A 2026 review of 36 trials found a median of about 35% of weight lost came from muscle-based measures across GLP-1 drugs. Resistance training and adequate protein help protect muscle.
How much muscle do you lose on Mounjaro or Zepbound?
Tirzepatide trials were included in the 2026 reviews, which found lean mass made up roughly 31–35% of weight lost on incretin drugs overall. Individual results vary widely, so measuring your own body composition with DEXA is the most reliable way to know.
What is the best way to measure muscle loss on a GLP-1?
A DEXA scan is the gold standard. It measures fat mass, lean mass by region, visceral fat and bone density in about 10 minutes, so you can compare scans over time.
How often should I get a DEXA scan on a GLP-1?
Get a baseline before or early in treatment, then rescan every 8–12 weeks at the same location so results are directly comparable.
How much does a DEXA scan cost?
On DEXASCAN.COM, DEXA, VO2 Max and RMR testing start at $89. Prices vary by location and are shown upfront before you buy. Body composition scans are usually self-pay; see is a DEXA scan covered by insurance?
Related reading
- Tirzepatide vs. semaglutide: why your DEXA scan is the honest scorecard
- Lose fat, not muscle in 2026: a data-driven guide
- How much does a DEXA scan cost in 2026? Prices by state
- Is a DEXA scan covered by insurance?
Find a DEXA scan near you
DEXASCAN.COM makes it easy to get your baseline. Every provider in our network is validated, prices are shown upfront, and you can buy online and get your booking instructions within minutes. DEXA, VO2 Max and RMR testing start at $89.
Sources: Batsis JA, et al. Systematic review of body composition changes with incretin-based therapies, Annals of Internal Medicine, 2026 (as reported by Healio); European Congress on Obesity 2026 posters 0408 and 0781 (as reported by Epocrates).
This article is for educational purposes and is not medical advice. Talk with your healthcare provider before starting or changing any medication, diet or exercise program.