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How to keep muscle while on GLP-1 weight-loss medicines

By Ingmar Lindström, family doctor (specialist in family medicine)

Published: · Last reviewed:

Short answer

When you lose weight on a GLP-1 medicine, you lose mostly fat but also some lean mass, which includes muscle.

The best-supported ways to protect muscle are regular strength training and enough protein, ideally together.

Talk to your prescriber (the doctor who prescribes your medicine) before you change anything.

See a physio or exercise professional if you are new to training.

Also see one if you have pain or a health condition.

This guide is general information.

It is not personal medical advice.

It does not cover medicine doses.

GLP-1 medicines include semaglutide, tirzepatide and liraglutide. You may know them by brand names such as Wegovy, Ozempic, Mounjaro or Saxenda. Ozempic is licensed for type 2 diabetes. This guide applies to all of them and does not compare them.

Do GLP-1 medicines make you lose muscle?

Some lean mass, yes.

  • In the STEP 1 trial of semaglutide, 95 people on the medicine had body scans.
  • Over 68 weeks they lost on average 8.4 kg of fat and 5.3 kg of lean mass (Wilding et al., NEJM 2021, appendix Table S5).
  • That is about 61% fat and 39% lean mass.
  • Lean mass is not only muscle. It also includes organs, bone and water (Neeland et al., 2024).
  • Lean mass went down, but its share of body weight went up by about 3 percentage points, because more fat was lost (same STEP 1 table).
  • Results vary between studies. Lean mass made up from about 15% or less to about 40-60% of the weight lost (Neeland et al., 2024).
  • Some researchers think the muscle that remains may work better. This is not settled (same source).

What we do not know yet: how much this loss affects strength and daily life in the long run.

Why does keeping muscle matter?

Muscle helps you stay strong, steady and independent.

Low muscle and bone mass are linked to falls, fractures, disability and a lower quality of life (joint advisory, 2025).

Who should pay most attention?

The advisory names older adults, people in perimenopause or menopause, people with lower testosterone, people who sit a lot or do no strength training, and people eating little protein.

What can I do this week?

  1. Tell your prescriber you want to protect your muscle.
  2. Ask whether anything in your health limits exercise.
  3. Book a first strength session, at home or in a gym. Short is fine.
  4. At each meal, eat the protein part first.
  5. Try a simple strength check you can repeat each month (below).

How do I do the 30-second chair check safely?

This is based on the 30-second chair stand used by doctors and physios (CDC STEADI; bpac NZ).

  • Use a sturdy chair with a straight back and no armrests.
  • Put the chair against a wall so it cannot move.
  • Have someone stand next to you.
  • Cross your arms over your chest.
  • Count how many times you fully stand up in 30 seconds.
  • Stop if you feel you might fall.
  • Skip the check if you already feel unsteady.
  • Write the number down. Compare it only with your own last result. It is not a diagnosis.

How much strength training do I need?

What do the guidelines say?

  • The World Health Organization advises all adults to do muscle-strengthening activity at moderate or greater intensity, for all major muscle groups, on 2 or more days a week (WHO guidelines, 2020).
  • For older adults, WHO adds varied activity with balance and strength training on 3 or more days a week, to help prevent falls (same source).
  • An NHS prescribing guide for GLP-1 medicines advises strength training at least twice a week, plus at least 150 minutes of moderate activity a week (NHS BSW ICB, 2026).
  • The joint advisory goes further: strength training at least 3 times a week, plus at least 150 minutes of moderate activity (joint advisory, 2025).
  • Aerobic activity alone does less to keep lean mass during fast weight loss. The plan should match your fitness and health (same source).

Strength training can use your bodyweight, resistance bands, machines or free weights.

Does massage help keep muscle?

Massage is not one of the advised ways to keep muscle.

The advisory names strength training and protein (joint advisory, 2025).

How much protein should I eat?

Who should check with a doctor first?

What does the evidence say?

The joint advisory says (2025):

  • Enough protein should be a priority, especially alongside strength training.
  • Protein alone is likely not enough to keep muscle without strength training.
  • There is no single agreed protein target for people living with obesity.

Ask your doctor or a dietitian for your own target.

How do I eat enough when I am not hungry?

The advisory suggests small, regular meals and protein first.

Easy options include fish, eggs, Greek yoghurt, cottage cheese, nuts and seeds.

Beans, peas and lentils are good plant sources.

When should I see a physio or exercise professional?

The advisory supports checking muscle strength and function, and referral to a physiotherapist or exercise physiologist where appropriate (2025).

General advice: it is a good idea to see one if:

  • You have never done strength training.
  • You have joint pain, back pain or an old injury.
  • You are older, have had a fall, or feel unsteady.
  • You have osteoporosis or low bone density.
  • Everyday tasks, such as stairs, are getting harder.

They can test your strength and set a plan that suits you.

When should I get medical help?

Call your local emergency number if you:

  • faint while exercising
  • have chest pain that does not go away
  • have chest pain and feel sweaty, sick, light-headed or short of breath
  • have severe difficulty breathing

(Based on NHS: fainting, NHS: chest pain, NHS: shortness of breath.)

See a doctor straight away if you have severe, long-lasting pain in your stomach area that may move to your back. With semaglutide, tirzepatide or liraglutide, this could be a sign of an inflamed pancreas (EU leaflet, semaglutide; EU leaflet, tirzepatide; EU leaflet, liraglutide).

If you use insulin or a sulphonylurea for diabetes, ask your doctor about low blood sugar.

The leaflets warn that the risk of low blood sugar can be higher when these are used with semaglutide, tirzepatide or liraglutide (same leaflets as above).

FAQ

Will I lose muscle on GLP-1 medicines?

Most people lose some lean mass along with fat, as with other large weight loss.

How much varies between people and studies.

How much protein should I eat on GLP-1 medicines?

There is no single agreed target.

Ask your doctor or a dietitian for your own target.

If you have kidney disease, talk to your doctor before eating more protein.

Is walking enough to keep muscle?

Walking is good for health.

Strength training protects lean mass better during fast weight loss.

How often should I do strength training?

WHO advises at least 2 days a week for all adults.

Guidance for people on GLP-1 medicines ranges from at least twice to at least 3 times a week.

Who can help me start safely?

A physiotherapist or exercise professional can check your strength and build a plan for you.

For clinics

Physio and exercise clinics are welcome to link to this guide or share it with clients.

Sources