Do You Lose Muscle on GLP-1 Drugs, and Can Exercise Stop It?

The short answer: Yes, some. In trials, about a quarter of the weight lost on tirzepatide was lean mass, and a similar share was lost with placebo. Strength training is the main proposed way to protect muscle, but we found no trial proving it works on these drugs. Follow your prescriber's advice.

• Weight loss on GLP-1 drugs includes some lean mass. In the STEP 1 body-composition substudy (140 adults, semaglutide 2.4 mg, 68 weeks), fat mass fell 19.3% and lean mass fell 9.7% [1].
• In the SURMOUNT-1 DXA analysis (160 adults, tirzepatide, 72 weeks), about 25% of weight lost was lean mass. The share was about the same in the placebo group [2].
• Across reviews, lean mass is roughly 15% to 40% of weight lost, depending on the drug, dose, starting body composition and time on treatment [4].
• "Lean mass" on a scan is not the same as muscle, and we do not yet know whether the loss harms strength or daily function [4].
• Resistance (strength) training is the usual recommendation. A 2024 review proposes it, and the evidence in people on these drugs is still limited [5].
• Loosn does not give medication or dosing advice. Follow your prescriber, and contact them for severe vomiting, dizziness, unusually fast weight loss or unusual pain [8].

Yes, some. Most of the weight you lose is fat, but a share is lean mass, which includes muscle.

Here are the main body-composition studies, with sample sizes. These scans use DXA (dual-energy X-ray absorptiometry), which splits body weight into fat and lean tissue.

In the tirzepatide analysis, about 25% of the weight lost was lean mass, with the rest fat, and the authors reported a similar split in both the tirzepatide and placebo groups [2]. A separate report on the same trial's DXA substudy presented at ObesityWeek 2022 found fat-to-lean ratios improved, meaning people lost proportionally more fat than lean tissue. It was a conference abstract, and the oldest age group (65 and over) had only 20 people [3].

A 2025 mini review put lean mass at roughly 15% to 40% of total weight lost across studies, and cited a real-world liraglutide cohort at about 22% [4]. The Diabetes Care review estimates the loss on these drugs at about 10% of lean mass, or around 6 kg (13 lb), which the authors compare to a decade or more of aging [5].

What this means: losing some lean mass is expected on these drugs. It is not a sign that something has gone wrong.

Not clearly. That is one of the more surprising findings.

In the SURMOUNT-1 DXA analysis, the share of weight lost as lean mass was about 25% in both the tirzepatide and placebo groups [2]. Placebo participants also lost some weight, and their lean mass fell too (-2.6%). That suggests part of the lean mass loss comes from losing weight in general, not only from the drug [2].

The picture is not settled. The studies above are small DXA subgroups, not the whole trial populations, and they did not compare the drug against a matched diet that gives the same weight loss. The 2025 review also says variation depends on drug, dose and duration [4].

No. A DXA scan's lean mass includes muscle, but also water, organs and other non-fat tissue. (This is general background, not from the sources above.) So a drop in lean mass overstates pure muscle loss, and changes in body water can move the number.

The more important question is whether any muscle lost matters for how you feel and function. The 2025 review calls it an open question whether the loss is adaptive or maladaptive, and it did not report strength or function results from GLP-1 trials. Its evidence on direct effects on muscle comes mainly from rodent and lab studies [4].

Muscle helps you stand up from a chair, climb stairs, carry groceries and stay steady on your feet. Losing strength along with weight could make daily tasks harder, especially as you get older. That reasoning is common sense, not proof that the lean mass lost on these drugs causes harm.

The Diabetes Care authors also suggest that preserving lean mass during treatment could help reduce weight and fat regain after the medicine stops. They present this as a suggestion rather than a proven result [5].

It may reduce it, but we cannot say it stops it. Here is what exists.

• A proposal from experts. The 2024 Diabetes Care review recommends tailored resistance training as an add-on to these drugs, with the aim of preserving lean mass while reducing fat. The authors call this a proposal rather than a proven treatment [5].
• A trial with liraglutide. In a Danish randomized trial, 195 adults with obesity first lost weight on an 8-week low-calorie diet (average 13.1 kg). They were then randomized for a year to exercise, liraglutide 3.0 mg, both, or placebo. Compared with placebo, weight regain was 9.5 kg lower with both, 6.8 kg lower with liraglutide and 4.1 kg lower with exercise. Body-fat percentage fell about 3.9 points with the combination, around twice as much as with either alone. The abstract we read did not report lean mass [6]. This tested liraglutide, an older GLP-1 drug, and was about keeping weight off, not directly about muscle.
• Other combined-treatment trials. The 2025 review describes a 2023 trial in which combined exercise and a GLP-1 drug reduced metabolic syndrome severity, abdominal obesity and inflammation more than either alone. We did not read that trial directly [4].
• Resistance training in general adults. The Diabetes Care review reports that supervised resistance training lasting more than 10 weeks increases lean mass by about 3 kg (6.5 lb) and strength by about 25% in men and women. That figure comes from studies outside GLP-1 treatment [5].

What this means: exercise is a sensible, low-risk bet for protecting muscle and function, supported by good reasoning and some related evidence. It is not yet proven that it prevents muscle loss in people on semaglutide or tirzepatide. We did not find a trial showing that.

Check with your prescriber first. Loosn does not give dosing or medication advice, and what is right for you depends on your health, your medicine and how you feel.

Here is what the sources say about exercise amounts:

• US guidelines advise muscle-strengthening activity on at least 2 days a week [9].
• The 2025 review suggests resistance training of 60 to 90 minutes a week, in 2 to 3 sessions of 20 to 30 minutes, using bands, weights or bodyweight exercises. It also recommends balance and mobility work, especially for older adults, and aerobic activity building toward 150 minutes of moderate activity a week [4].

Choose moves that train the big muscles of the legs, hips, back and chest. These three are common starting points. Doses are a clinical starting point, not from a trial. Start light, and skip any move that causes joint or sharp pain.

1. Goblet squat. 

Hold a light weight at your chest and squat to a comfortable depth, or to a chair. Do 2 sets of 8 to 10. See our goblet squat.

1. Romanian deadlift. 

Hold light weights, push your hips back with a soft knee bend and a flat back, then stand. Do 2 sets of 8 to 10. See our Romanian deadlift.

1. Incline push-up. 

Hands on a counter or sturdy bench, lower your chest and press back. Do 2 sets of 6 to 10. See our incline push-up.

Rest 1 to 2 minutes between sets; our exercise rest timer can help. Train 2 to 3 non-consecutive days a week. If you feel dizzy, weak or nauseated, do a lighter session or rest. Mild muscle soreness is normal. Sharp pain, a swollen joint or pain that is worse the next day is a signal to scale back.

For more on training safely on these medicines, see our guide to exercise on GLP-1 medication and our GLP-1 companion programme. If you are returning to exercise after a break, our return to exercise guide can help. For the basics, see our glossary entry on strength.

Kai, Loosn's AI physio coach, can help you pace strength sessions around how you feel. It does not replace advice from your prescriber or an assessment if your symptoms are severe, getting worse or unusual.

Protein matters, but we cannot give you a number from the sources we read.

A 2025 joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society advises getting sufficient protein to limit lean mass loss. As reported, it notes that protein intake is at risk when stomach side effects reduce how much you eat, and it recommends including resistance training. It gave no numeric protein target in the summary we read [7]. Ask your prescriber or a registered dietitian what is right for you.

Quite a lot is unknown:

• Most of the data come from DXA subgroups of a few hundred people at most, and some were conference abstracts [1][3].
• Lean mass on a scan is not pure muscle, and strength and function results from these trials were not reported in what we read [4].
• It is unclear whether the lean mass lost is harmful, and for whom [4].
• We did not find a trial showing that strength training preserves muscle in people on semaglutide or tirzepatide. The best evidence is indirect [5][6].
• No source we read gives a proven protein target for people on these drugs [7].
• Newer drugs and higher doses are still being studied, so these numbers may change.

Follow your prescriber's instructions. Loosn gives no medication or dosing advice and is not a diagnosis tool.

Call 911 (or your local emergency number) if [8]:

• you have signs of a serious allergic reaction: swelling of the face, lips, tongue or throat, wheezing, chest or throat tightness, or trouble breathing, swallowing or talking
• you faint, or have severe dizziness that does not settle
• you have severe stomach or back pain with severe nausea or vomiting, which can signal pancreatitis (the source describes it as "severe and sometimes deadly")

(Other common emergency numbers are 999 in the UK, 112 across the EU and 000 in Australia.)

Contact your prescriber the same day if [8]:

• you cannot drink liquids, or have vomiting or diarrhea that will not stop
• you cannot pass urine, or notice a change in urination
• you have pain in the upper right belly, right shoulder or between the shoulder blades, dark urine, yellow skin or eyes, or fever with chills
• you notice changes in your eyesight
• you have signs of low blood sugar, such as dizziness, shakiness, sweating, confusion or a fast heartbeat

Tell your prescriber soon if:

• your weight is dropping faster than expected, or you feel weak or very tired
• you have new or unusual pain, including hip or pelvic pain, burning, numbness or tingling [8]
• you have a neck lump, hoarseness that will not go away, or trouble swallowing [8]
• joint or back pain is getting worse as you lose weight or start exercising
• you have questions about your dose, protein or exercise, which are decisions for you and your prescriber

Loosn is not a substitute for assessment when symptoms are severe, getting worse or unusual.

Does Ozempic cause muscle loss? 

Weight loss on Ozempic and similar drugs includes some lean mass, which is mostly muscle plus water and organs. In a semaglutide 2.4 mg substudy of 140 adults, lean mass fell 9.7% over 68 weeks [1]. Whether this harms strength or function is not yet known [4]. Lean mass also falls with ordinary weight loss, so the drug is not the only factor.

How much of the weight you lose on GLP-1 drugs is muscle? 

Often around a quarter, but estimates vary. In a tirzepatide substudy of 160 people, about 25% of weight lost was lean mass, and the placebo group had a similar share [2]. A 2025 review puts it at roughly 15% to 40% across studies, depending on the drug, dose, starting body composition and duration [4]. These figures come from body scans, not strength tests.

Can exercise prevent muscle loss on GLP-1 drugs? 

Exercise may reduce it, but this is not proven for people on these drugs. A 2024 Diabetes Care review proposes tailored resistance training as an add-on [5]. A Danish trial of 195 adults found exercise plus liraglutide kept more weight off than either alone [6]. We did not find a trial showing strength training preserves muscle on semaglutide or tirzepatide.

How much protein do you need on a GLP-1 drug? 

There is no number we can responsibly give you. A 2025 joint advisory from four US nutrition and obesity groups advises getting sufficient protein to limit lean mass loss, and notes that stomach side effects can cut how much you eat [7]. As reported, it gave no numeric target. Ask your prescriber or a registered dietitian what is right for you.

How often should I strength train on a GLP-1 drug? 

US guidelines advise muscle-strengthening activity on at least 2 days a week [9]. A 2025 review suggests 2 to 3 sessions of 20 to 30 minutes using bands, weights or bodyweight [4]. Start lighter than you think you need, build slowly, and check with your prescriber first, especially if you feel unwell, dizzy or have joint pain.

When should I call my prescriber? 

Contact your prescriber if you cannot drink liquids, have vomiting or diarrhea that will not stop, feel severely dizzy or faint, or notice changes in urination [8]. Severe stomach or back pain, with severe nausea or vomiting, can signal pancreatitis, which needs urgent care [8]. Tell them too about weight dropping faster than expected, or new pain.

Download the Loosn app for plain-language tips on strength, joints and staying active on GLP-1 medication. If you want guided help pacing your sessions, see how Loosn works and meet Kai, Loosn's AI physio coach.