Do GLP-1 medicines cause muscle loss?
Made with AI tools and overseen by an Australian GP · Updated 8 November 2026
“Ozempic melts your muscles” makes a great headline. The evidence is more boring and more useful: some lean tissue goes with the fat, and you can do something about it.
Quick answer: Some of the weight lost on GLP-1 medicines is lean tissue, which includes muscle. Across trials it averages about a quarter of the weight lost, and up to about 40% in some studies. Fat makes up most of the loss. Enough protein and regular strength training are the best-supported ways to protect muscle.
What the evidence shows
- A 2024 analysis of 22 trials found lean mass made up about 25% of the weight lost on GLP-1 medicines. Lean mass as a share of the body didn’t fall.
- In semaglutide studies, lean tissue ranged from almost none to about 40% of the weight lost. Because fat fell more, lean tissue as a proportion of the body went up.
- The strongest medicines (semaglutide 2.4 mg, tirzepatide 15 mg) caused the most fat loss but were among the least muscle-sparing.
- Reviews estimate lean mass falls by about 10% (around 6 kg) over a 68–72 week course.
- “Lean mass” on a scan includes muscle, organs and water, so it isn’t all muscle. Whether the loss affects strength and day-to-day function long term is still being studied.
Protein
- The usual adult recommendation is about 0.8 g of protein per kg of body weight a day.
- Experts have proposed higher targets during active weight loss, around 1.2–1.6 g/kg a day. The best target for people living with obesity isn’t settled, partly because using total body weight can overestimate needs.
- Long-term intake above 2 g/kg a day isn’t advised.
- Small appetite? A dietitian can help, and a supplement drink may be useful if you can’t eat enough.
- If you have kidney disease, check with your doctor before increasing protein.
Strength training
- Resistance (strength) training, or a mix of strength and aerobic exercise, is well established to help preserve lean mass during weight loss. Aerobic exercise alone does less.
- Supervised strength programmes lasting more than 10 weeks have added about 3 kg of lean mass and about 25% more strength.
- In one trial, a GLP-1 medicine plus exercise preserved bone density, while the medicine alone reduced it.
- Older adults have the most to lose: keeping muscle helps protect against frailty. See our exercise handouts.
See your GP if you’re losing weight very fast, feel weak or dizzy, or are struggling to eat enough. Get urgent help (000 in Australia, or your local emergency number) if you faint or can’t keep fluids down.
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Common questions
Is the weight lost on Ozempic mostly fat?
Yes. On average about three-quarters is fat and about a quarter is lean tissue, which includes muscle, organs and water.
How much protein should I eat on a GLP-1 medicine?
The usual adult recommendation is about 0.8 g per kg of body weight a day, and experts suggest more during active weight loss, around 1.2–1.6 g/kg. Ask your doctor or a dietitian for a target that suits you, especially if you have kidney disease.
Do I need protein shakes?
Not usually. Food comes first. A supplement drink can help if nausea or a small appetite means you can’t eat enough protein.
Is walking enough to protect muscle?
Walking is good for your heart and mood, but aerobic exercise alone does less for muscle. Adding strength training is better supported.
Are older people more at risk of muscle loss?
Yes. Muscle naturally declines with age, and keeping it matters for avoiding frailty, so strength training and enough protein are especially important.
Evidence and more information
- Karakasis et al, Metabolism 2024: GLP-1 medicines and body composition, systematic review and network meta-analysis of 22 trials
- Bikou et al, Expert Opinion on Pharmacotherapy 2024: Systematic review of semaglutide and lean mass
- Locatelli et al, Diabetes Care 2024: Incretin weight-loss medicines and resistance exercise
- Mechanick et al, Obesity Reviews 2024: Strategies for minimising muscle loss on incretin medicines
- Mozaffarian et al, 2025: Nutritional priorities to support GLP-1 therapy for obesity (joint advisory of four US obesity and nutrition societies)
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