Here's the short version. Semaglutide, the drug in Ozempic, causes large weight loss, and part of that loss is lean tissue [2]. The newest MRI data suggest the muscle that remains carries less fat [1]. These findings do not establish a muscle-building effect; preserving strength requires a separate plan.
Does Ozempic burn muscle?
Some of the weight lost on semaglutide is lean mass, as with any large weight loss. A 2024 review of GLP-1 trials found the lean share ranged widely: about 15% or less of weight lost in some studies, 40% to 60% in others [2].
The reviewers point to differences in who was studied, which drug was used and other health conditions [2]. So a single headline number for "muscle lost on Ozempic" doesn't exist.
Lean mass is not the same as muscle
DXA lean soft tissue includes organs, fluids and water inside fat tissue, with bone mineral reported separately [2]. When you lose a lot of weight, some of that "lean" drop is water and organ size, not muscle.
That's why MRI matters. It can measure the muscle itself, and the fat marbled through it. Based on MRI studies, the review authors describe muscle changes on GLP-1 drugs as adaptive: roughly what you'd expect for the weight lost, with better muscle quality [2].
What MRI showed about the muscle itself
STEP UP tested semaglutide 7.2 mg (the strength sold as Wegovy HD), 2.4 mg and placebo for 72 weeks in adults with obesity [1]. Its MRI analysis covered 55 people with a valid first scan: 49 on semaglutide and 6 on placebo.
| Study | Population | Measure | Finding | Strength of evidence |
|---|---|---|---|---|
| Hjelmesæth 2026, STEP UP MRI analysis | Adults with obesity, 55 with scans, 72 weeks | MRI | Body fat −11.7 quarts (−11.1 L) vs placebo; thigh muscle −1.2 quarts (−1.1 L), not statistically clear (p=0.07); fat inside thigh muscle −0.92 points; sit-to-stand held | Small subgroup, 6 on placebo; Novo Nordisk-run trial |
| Neeland 2024 review | GLP-1 drug trials | DXA and MRI | Lean share of weight lost from about 15% to 40–60%; MRI suggests adaptive change | Review |
Differences are semaglutide vs placebo [1] [2]. The trial's maker, Novo Nordisk, employed several of the STEP UP authors.
Fat fell far more than muscle. The thigh-muscle drop wasn't statistically clear, and the fat inside the muscle fell by a clear margin [1]. People averaged 13 sit-to-stand repetitions in 30 seconds at the start and 15 at week 72.
With six people on placebo, this is early evidence. It fits the review's picture, though, and it's the closest look yet at what happens inside the muscle.
Can you gain muscle while on it?
Gaining muscle in a calorie deficit is possible for some people, mainly newer lifters, but no semaglutide trial has tested it. That's reasoning from exercise science, not a trial finding.
The catch is appetite. Semaglutide cuts how much you eat, and building muscle needs enough protein and energy to recover from training. If you eat very little, gains are harder.
How people keep muscle on semaglutide
Resistance training and enough protein are the levers with trial support. In a meta-analysis of 49 trials and 1,863 adults, adding protein to resistance training increased gains in strength and fat-free mass [3].
Those trials weren't in people on GLP-1 drugs, and the extra gain was modest [3]. Your prescriber or a registered dietitian sets protein needs that fit your weight, age and kidneys.
| Habit | Evidence | Next step |
|---|---|---|
| Resistance training | Trial support in adults; the main driver of muscle gain | Ask your clinician which program suits your joints and fitness |
| Protein with training | Morton 2018 meta-analysis of 49 trials | Ask a dietitian for a daily target |
| Tracking body composition | MRI and DXA studies show fat and lean change separately | Ask whether a scan is worth doing for you |
Who should take extra care with muscle
Older age and more severe illness raise the risk of sarcopenia, the age-related loss of muscle and strength. The 2024 review flags both as reasons to choose candidates for these drugs carefully [2].
If you're over 65, already frail, or recovering from an illness, ask your prescriber how they'll watch strength and function. A simple chair-stand test or grip test at each visit is one way. The review also discusses medicines being studied to protect muscle; that discussion is not proof of benefit from an available add-on treatment [2].
Ozempic vs Wegovy for this question
Both are semaglutide. Ozempic is labeled for type 2 diabetes, including heart and kidney risk reduction in people with diabetes [4]. Wegovy is labeled to reduce excess weight and keep it off, among other uses [5].
So muscle questions during weight loss usually involve Wegovy doses. The STEP UP data above come from Wegovy-strength doses, not Ozempic doses.
If body composition is your goal
Start with the body-composition shortlist. Tirzepatide has its own body-scan data, covered in can you build muscle on tirzepatide. For the unapproved triple agonist people ask about, see what retatrutide's body-scan study showed.
If blood sugar and heart health matter more than the scale, the metabolic shortlist is the better start. For another common question, see whether semaglutide helps with inflammation.