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Do GLP-1 medicines cause muscle loss and loose skin?

Muscle loss and loose skin after weight loss on Ozempic, Wegovy or Mounjaro: what body-scan trials measured, how it compares with dieting and surgery, and what guidelines say about protein and strength training.

GLP Guidebook teamPublished 5 Oct 202615 min read25 sourcesWritten from published sources

Written for India. Reading from the US? US versionComing soon

The short answer

Yes, some. In body-scan trials, lean mass made up about 25% to 40% of the weight lost on tirzepatide or semaglutide. Lean mass includes muscle, water and organs. Dieting and weight-loss surgery take a similar share. Loose skin is reported more often the more weight people lose, and exercise cannot remove it.

Key takeaways

  • GLP-1 medicines take some lean mass with the fat, about 2 in every 5 kg lost on semaglutide 2.4 mg and 1 in 4 kg on tirzepatide.3,4
  • Diet-only weight loss also takes lean mass, and many dieting studies report about 25% of the weight lost as lean mass.3,5
  • In a 2026 survey of 1,226 patients, saggy skin was reported by 15% who lost under 10% of their weight and 72% who lost over 20%.17
  • Guidelines name strength training and enough protein to protect muscle, and ICMR sets the protein allowance for healthy Indian adults at 0.83 g per kg a day.4,15
  • The US Wegovy label reports more hip and pelvis fractures in people aged 75 or older, at 2.4% on Wegovy vs 0.6% on a dummy injection.8
On this page
  1. Do GLP-1 medicines cause muscle loss?
  2. How does that compare with dieting or bariatric surgery?
  3. Does losing lean mass make people weaker?
  4. What about older adults and sarcopenia?
  5. Why does muscle matter more for many Indians?
  6. What do guidelines say about protein and strength training?
  7. Do GLP-1 medicines cause loose skin?
  8. Can loose skin after weight loss be prevented or fixed?
  9. Questions people ask
  10. How we researched this
Before you go further
  • GLP-1 medicines are prescription-only. A government statement on 1 Apr 2026 said only endocrinologists, internal-medicine specialists and cardiologists can prescribe them.23 CDSCO expert-committee minutes attach a similar condition to some approvals (endocrinologist or internal-medicine specialist), but we found no rule covering every brand.24,25
  • They have serious risks as well as common side effects: Guide 5: Side effects and risks.
  • Trial figures here are group averages. They are not a promise for any one person, and this page doesn't say who these medicines suit.

Do GLP-1 medicines cause muscle loss?

Yes, some. Body scans in two big trials found that 1 in 4 to 2 in 5 kg lost was lean mass.

The trials measured this with DXA scans, a low-dose X-ray that splits the body into fat, bone and lean tissue.11 Lean mass is not the same as muscle. It also counts organs, ligaments, tendons and water.3 One expert advisory estimates muscle is about half of lean mass.4

Semaglutide 2.4 mg (STEP 1). This is the Wegovy dose. A substudy scanned 140 people over 68 weeks.1 Fat mass fell 19.3% and lean mass fell 9.7%.1 Of 13.6 kg lost on average, 8.3 kg was fat and 5.3 kg (38%) was lean.4 That works out to about 20% of the weight lost being muscle.4

Tirzepatide (SURMOUNT-1). This is the medicine in Mounjaro (what is tirzepatide?). A substudy scanned 160 people over 72 weeks.3 Weight fell 21.3%, fat mass 33.9% and lean mass 10.9%.3 About 75% of the weight lost was fat and 25% was lean.3 Eli Lilly, which makes Mounjaro, funded the analysis.3 How much weight people lose in the full trials is in how much weight people lose on Ozempic or Mounjaro.

Take a 90 kg person who lost 15%, or 13.5 kg. That means about 3 to 5 kg of lean mass. Roughly half of that would be muscle. This is our arithmetic from the averages above, not a forecast.

The US Wegovy label agrees. It says semaglutide "lowers body weight with greater fat mass loss than lean mass loss".8 If GLP-1 is a new term, what GLP-1 stands for explains it. The link between semaglutide, Wegovy and Ozempic is in is semaglutide the same as Ozempic?

RisksThe risks, in brief
  • Stomach effects are common. Nausea, diarrhoea, vomiting, constipation and stomach pain lead the labels' lists.8,9
  • Pancreatitis (an inflamed pancreas) is a label warning. The sign is severe stomach pain that won't go away.8,9
  • Gallbladder problems, such as gallstones, are in both labels.8,9
  • Low blood sugar is more likely when taken with insulin or a sulfonylurea, a type of diabetes tablet.8,9
  • Dehydration from vomiting or diarrhoea can injure the kidneys.8,9
  • Thyroid warning. Ruled out by the US labels for people with a personal or family history of MTC, a thyroid cancer, or MEN 2; tell your doctor if this applies.8,9 The Wegovy label says to stop at least 2 months before a planned pregnancy.8
Full detail in Guide 5: Side effects and risks →
Get help now: call 112. Call for severe stomach pain that won't go away, with or without vomiting.8 The pain can spread to your back.8

How does that compare with dieting or bariatric surgery?

The share of lean mass lost on GLP-1 medicines is in the same range as dieting and weight-loss surgery. Losing a lot of weight by any route takes some lean tissue.

A joint US nutrition advisory says these losses grow with the amount of weight lost.4 It adds that they are similar to bariatric surgery and very low-calorie diets.4 Speed of loss, the size of the calorie cut and strength training also play a part.4

RouteStudyLean share of weight lost
Semaglutide 2.4 mgSTEP 1 substudy, 140 people, 68 weeks138% to 40%4,3
TirzepatideSURMOUNT-1 substudy, 160 people, 72 weeks3About 25%3
Dummy injection plus lifestyle adviceSame SURMOUNT-1 substudy, placebo group3About 25%3
Very low-calorie diet127 people, 430 kcal a day, 8 weeks525%5
Bariatric surgeryReview of surgery studies using DXA314% to 45%3

Bariatric figure: the review found 55% to 86% of weight lost was fat; the lean share is our subtraction. STEP 1 is reported as 38% by one source and 40% by another. These studies were not compared head to head, so the rows don't show that one route spares more muscle.

In SURMOUNT-1, the people on the dummy injection lost the same 25% share of lean mass as those on tirzepatide.3 They lost far less weight overall.3 Weight-loss surgery and how it compares with medicines has its own post: Bariatric surgery vs GLP-1 medicines. All the options sit side by side in Guide 3: your options.

Does losing lean mass make people weaker?

In the trials, people on these medicines reported better physical function. Strength data are thin, though, and some groups lose more muscle than others.

In STEP 1, people on semaglutide reported a bigger rise in physical functioning than those on the dummy injection.2 The tirzepatide substudy found the same, "despite decreases in lean mass".3 Because fat falls faster than lean mass, lean tissue makes up a bigger share of the body afterwards.1,6 A 2026 review of 7 trials put that rise at about 2 percentage points.6

Studies that measured muscle strength "generally found no significant change", a 2026 review found.7 In a 2026 survey of US patients, 33% who lost over 20% of their weight reported feeling less strong.17,18 Among those who lost under 10%, it was 9%.17

Some people are at higher risk of losing muscle. The advisory names older age, menopause, low testosterone, inactivity and no strength training.4 Its modelling suggests muscle is 10–15% of the weight women lose and 20–25% for men, without strength training.4

What about older adults and sarcopenia?

Lean mass naturally falls with age.3 Older adults are also among the least studied groups, and direct evidence in them is scarce.7

Sarcopenia is muscle wasting that can come with age.15 Sarcopenic obesity means having sarcopenia and obesity at the same time.13 A 2026 review found muscle made up as much as 8.5% to 24.5% of weight lost, depending on the study, on GLP-1 medicines.7 Only 4 of its 21 studies looked at older adults.7 The authors say the evidence is "insufficient" to judge older adults' risk of muscle loss.7

In the tirzepatide substudy, people aged 65 or older lost about 76% of their weight as fat.3 That matched younger groups, but the age groups were small and the analysis was done after the fact.3

Few very old people were in the Wegovy weight trials. Only 23 people on Wegovy, 1%, were aged 75 or older.8 A separate heart trial counted hip and pelvis fractures. In people aged 75+, they hit 2.4% on Wegovy vs 0.6% on placebo.8 For women of all ages, the figures were 1% vs 0.2%.8

WHO advises older adults to do balance and strength activity on 3 or more days a week. One aim is to prevent falls.16 More on age and other "when not to" questions is in Guide 4: should I consider a GLP-1?

Free toolQuestions to ask your doctor about muscle, age and side effects

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Open the question list

Why does muscle matter more for many Indians?

Many Indians carry more body fat and less muscle at the same BMI than white people. Losing lean mass starts from a smaller base.

Doctors call a normal BMI with high body fat the "thin-fat" body type.11 It comes with more fat around the organs (visceral fat) and less lean mass.11 A 2004 comparison made the point with two doctors of the same BMI, 22.3.11 The Indian doctor had 21.2% body fat; the white (Caucasian) doctor had 9.1%.11

India uses lower BMI cut-offs for this reason. Healthy is 18.0–22.9, overweight 23–24.9, and obesity 25 or more.14 The Endocrine Society of India puts the thin-fat type at about 15% of people in Chennai and 16% in Mumbai.12 Check your own numbers against these cut-offs in Guide 1: weight and health in Indians.

Low muscle is common in India too. In India's national ageing survey (LASI), 42% of 72,250 older adults had possible sarcopenia.13 About 9% had sarcopenic obesity.13 A 2026 Indian expert consensus on these medicines cites sarcopenia rates of 14–39% in Indian adults with malnutrition or obesity.10 It calls for structured nutrition support, "especially for Asian Indians".10 That consensus was funded by Abbott Nutrition International, India.10

We found no published study of muscle loss on GLP-1 medicines in Indian patients. The thin-fat body type gets its own post: "Thin-fat" Indians.

What do guidelines say about protein and strength training?

Guidelines name strength training and enough protein as the two ways to protect muscle while losing weight. They describe general targets; a doctor or dietitian sets an individual one.

Strength training. Strength or mixed (strength plus aerobic) training is "well established" to help keep lean mass during weight loss.4 Aerobic exercise alone, like walking, does less for lean mass.4 Three sets of advice are below.

  • WHO (all adults): muscle-strengthening for all major muscle groups on 2 or more days a week.16
  • ICMR-NIN (India): 2 to 3 weight-bearing sessions a week, and regular training with weights to keep muscle.15
  • US nutrition advisory (people on GLP-1 medicines): strength training 3 or more times a week. Add at least 150 minutes of moderate aerobic activity, adjusted to fitness.4

The trials themselves did not test this. SURMOUNT-1 advised 150 minutes of activity a week "without a specific strength training protocol".3 The advisory cites one randomised trial where adding exercise to a GLP-1 medicine protected bone density.4 Most other support comes from look-back studies.4

Protein. ICMR sets the allowance for healthy Indian adults at 0.83 g per kg of body weight a day.15 The advisory notes that 1.2–1.6 g per kg has been proposed during active weight loss.4 The Indian consensus cites studies using 1.2–1.5 g per kg, and up to 1.6 g only with normal kidney function.10 ICMR adds that intakes above about 1.6 g per kg do not add muscle in strength training.15 The advisory says to avoid 2 g per kg or more over the long term.4

For a 70 kg adult, 0.83 g per kg is about 58 g a day. At 1.2–1.6 g per kg, it is 84–112 g. This is our arithmetic. Using actual weight can overstate protein needs in people with obesity, the advisory warns.4 Indian vegetarian protein is covered in Guide 8: life on a GLP-1. A full post is on the way: Protein on a GLP-1, and Indian sources. Exercise gets its own post: Exercise on a GLP-1.

Do GLP-1 medicines cause loose skin?

Loose skin post weight loss is tied most to how much weight comes off, on these medicines and after surgery alike. Age and speed may also matter.

A 2026 review found that weight loss on these medicines often brings visible skin changes, including less elastic skin.19 A 2026 survey asked 1,226 US patients on weight-loss medicines about their skin.17,18 Saggy skin rose steadily with the amount of weight lost.17

Reported saggy skin, by amount of weight lost
% of survey respondents · 1,226 US telemedicine patients on weight-loss medicines
Groups: 380, 395 and 325 people. Self-reported in a voluntary survey of mostly white women in the US; how fast people lost weight was not recorded. Rao et al. and Santiago Mangual et al., 2026. Checked 5 October 2026.17,18

Loose skin is also very common after weight-loss surgery. In one study, 57 of 64 people (89%) had sagging skin after surgery.20 A review says excess skin affects up to 96% of people after bariatric surgery.21

A 2026 review of 40 studies of GLP-1 medicines and skin listed the risk factors.19 They were older age, a long history of obesity, rapid weight loss, poor hydration and low protein.19 The big survey did not record how fast people lost weight, so its data can't test speed.18 Changes in the face have their own post: What is "Ozempic face"?.

Can loose skin after weight loss be prevented or fixed?

Exercise cannot remove loose skin after fat loss, however the weight came off. Surgery can, with real risks. We found no trial of a way to prevent it.

The skin review recommends gradual weight loss, good nutrition, hydration and early skin treatment.19 We found no trial that tested them. We found no study showing how much loose skin tightens on its own over time.

Building muscle does not remove spare skin. The UK's NHS says excess skin from "losing a lot of weight" "cannot be removed through exercise".22

What surgery involves. The NHS describes a tummy tuck (abdominoplasty), which cuts away loose skin and fat from the belly.22 It is usually only done at a healthy BMI, so it comes after weight loss, not instead of it.22 People need about 4 to 6 weeks off work and exercise.22 It leaves a scar across the lower belly.22 The NHS treats it as cosmetic, so it is not usually free there.22 We don't link to surgeons or clinics.

Questions people ask

Does Mounjaro cause muscle loss?

Some. In the SURMOUNT-1 body-scan substudy, about 25% of the weight lost on tirzepatide, the medicine in Mounjaro, was lean mass. People on the dummy injection lost the same share, but less weight overall.3

Does Ozempic cause loose skin?

Loose skin is linked to the amount of weight lost. A 2026 survey asked people on weight-loss medicines about saggy skin. It was reported by 72% who lost over 20% of their weight, vs 15% who lost under 10%.17

Does loose skin go away after weight loss?

We found no study that tracked whether loose skin tightens by itself over time. The UK's NHS says excess skin from losing a lot of weight cannot be removed through exercise.22

How do you lose fat without muscle loss?

Guidelines name strength or mixed training and enough protein as the main ways to limit muscle loss during weight loss. WHO advises muscle-strengthening activity on 2 or more days a week.4,16

How much protein do guidelines suggest during weight loss?

ICMR's allowance for healthy Indian adults is 0.83 g per kg a day. Higher targets of 1.2 to 1.6 g per kg have been proposed during active weight loss. An Indian consensus cites studies using up to 1.6 g only with normal kidney function.4,10,15

Can a home scale show muscle loss?

Trials measured fat and lean mass with DXA scans.1,3 A review notes DXA is expensive and mostly used in research settings.11

How we researched this

We read the body-scan analyses from STEP 1 (conference abstract) and SURMOUNT-1 (full paper). We also read the US Wegovy and Mounjaro labels and two 2026 reviews. We read the US nutrition advisory, the Indian consensus, ICMR-NIN's 2024 guidelines and WHO's 2020 activity guidelines in full.

For loose skin, we read a 2026 survey and its companion paper and a 2026 skin review. We also read two surgery papers and the NHS page. Most skin evidence is surveys and reviews, not trials. We say so in the text.

We cut several claims we could not source. We found no Indian study of muscle loss on these medicines, and no trial of creams or skin devices. We left out Ozempic's diabetes-dose body-scan data because the table we found was unclear.

Before you move on

  • Lean mass was about 25% to 40% of weight lost in the body-scan trials, similar to dieting.
  • Lean mass includes water and organs; muscle is roughly half of it.
  • Older adults and people with little muscle are least studied and may have most to lose.
  • Loose skin rises with the amount of weight lost; exercise doesn't remove it.
Side effects and risksI'm already on itDoctor questions

More from the India blog

INIndiaComing soonWhat is "Ozempic face", and can it be prevented? INIndiaHow much weight do people lose on Ozempic or Mounjaro? INIndiaComing soonProtein on a GLP-1: how much, and where Indians get it
About GLP Guidebook

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An independent guide to GLP‑1 medicines. We don't sell medicines, take drug-company money or earn clinic commissions. Once a month: new brands, price changes, approvals and recalls. How we write

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Sources

  1. Wilding JPH et al. Impact of semaglutide on body composition in adults with overweight or obesity: exploratory analysis of the STEP 1 study. Conference abstract, 2021. Abstract (PDF)
  2. Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med 2021;384:989–1002. doi:10.1056/NEJMoa2032183 · PMID 33567185
  3. Look M et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight. Diabetes Obes Metab 2025. Funded by Eli Lilly. PMC11965027 · doi:10.1111/dom.16275 · PMID 39996356
  4. Mozaffarian D et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory (ACLM, ASN, OMA, TOS). Am J Clin Nutr 2025;122:344–67. doi:10.1016/j.ajcnut.2025.04.023
  5. Willoughby D, Hewlings S, Kalman D. Body composition changes in weight loss: strategies and supplementation for maintaining lean body mass. Nutrients 2018;10:1876. doi:10.3390/nu10121876 · PMC6315740
  6. Laverde LP et al. Effect of GLP-1 receptor agonists at doses for obesity management on muscle health: systematic review and meta-analysis of RCTs. Int J Obes 2026. doi:10.1038/s41366-026-02118-y
  7. Jagasia K, Pfeiffer AM, Vitale K. GLP-1 receptor agonist therapy and skeletal muscle: a narrative review with implications for older adults. J Aging Res Lifestyle 2026. doi:10.1016/j.jarlif.2026.100083
  8. Wegovy (semaglutide) US Prescribing Information and Medication Guide, revised 06/2026. US label, not the Indian one. novo-pi.com/wegovy.pdf
  9. Mounjaro (tirzepatide) US Prescribing Information, revised 08/2026. US label, not the Indian one. pi.lilly.com/us/mounjaro-uspi.pdf
  10. Joshi SR, Misra A, Mithal A et al. Nutritional considerations for glucagon-like peptide-based therapies: an Asian Indian consensus recommendation. Obes Pillars 2026. Supported by Abbott Nutrition International, India. doi:10.1016/j.obpill.2026.100296
  11. Kapoor N. Thin fat obesity: the tropical phenotype of obesity. In: Endotext. MDText.com. NCBI Bookshelf NBK568563 · PMID 33734655
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  13. Verma M, Kapoor N, Chaudhary A et al. Prevalence and determinants of sarcopenic obesity in older adults: LASI Wave 1 (2017–18). Adv Ther 2022;39:4094–113. doi:10.1007/s12325-022-02216-z
  14. Misra A et al. Consensus statement for diagnosis of obesity, abdominal obesity and the metabolic syndrome for Asian Indians and recommendations for physical activity, medical and surgical management. J Assoc Physicians India 2009;57:163–70. PMID 19582986
  15. ICMR-National Institute of Nutrition. Dietary Guidelines for Indians, 2024 (protein pp. 75, 77; physical activity p. 88 of the PDF). nin.res.in (PDF)
  16. Bull FC et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med 2020;54:1451–62. doi:10.1136/bjsports-2020-102955 · PMC7719906
  17. Rao S, Midura I, Santiago Mangual KP et al. Skin impacts and tradeoffs of GLP-1 therapy. Dermatol Ther (Heidelb) 2026. doi:10.1007/s13555-026-01882-z
  18. Santiago Mangual KP et al. Aesthetic, muscle, and dermatologic effects of medical weight management: patient-reported outcomes. Int J Womens Dermatol 2026. doi:10.1097/jw9.0000000000000283
  19. Barone M et al. Effects of GLP-1 receptor agonists on skin quality: a comprehensive literature review. Aesthetic Plast Surg 2026. doi:10.1007/s00266-026-05820-4
  20. Aldaqal SM et al. Post-bariatric surgery satisfaction and body-contouring consideration after massive weight loss. N Am J Med Sci 2013;5:301–5. doi:10.4103/1947-2714.110442 · PMC3662098
  21. Sadeghi P et al. Post-bariatric plastic surgery: abdominoplasty, the state of the art in body contouring. J Clin Med 2022;11:4315. doi:10.3390/jcm11154315 · PMC9330885
  22. NHS (UK). Tummy tuck (abdominoplasty). Page last reviewed 29 Sep 2023. nhs.uk
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Last checked 5 Oct 2026 · Next review due 5 Oct 2027 · Report an error

How this post was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to a qualified doctor before starting, stopping or changing any medicine, or starting a new exercise plan. How we write