The Weight Loss Atlas

Exercise and strength training

Quick answer. Exercise is one of the few add-ons tested alongside a GLP-1 medicine in a year-long trial. In that trial of liraglutide, adding exercise improved fat loss and fitness more than the medicine alone. Experts say strength training is the type that best protects muscle during weight loss. The Atlas did not find completed trials of specific programs in people taking semaglutide or tirzepatide, though one is running.

What it is

People lose muscle as well as fat when they lose weight, and GLP-1 medicines are no exception. Body scans in the big trials show that lean mass falls along with fat. Lean mass is not just muscle, since it includes organs, water and bone, so the drop does not always mean the same amount of muscle lost.

Exercise is the main tool people use to protect muscle. Two kinds matter. Aerobic exercise, such as walking, cycling or swimming, raises your heart rate and builds fitness. Strength training, also called resistance training, works muscles against weights, bands or your body weight.

The question for this page is which kind helps most while on the medicine, and how much of the answer comes from tests rather than opinion.

Trial evidence

What trials show

The most useful randomized trial is from Denmark. It enrolled 195 adults with obesity who had lost an average of 13.1 kg on an 8-week low-calorie diet. They were then randomized for one year to moderate-to-vigorous exercise, liraglutide 3.0 mg daily, both, or neither. Compared with the placebo group, they lost a further 4.1 kg with exercise, 6.8 kg with liraglutide and 9.5 kg with both.

The combination group lost 5.4 kg more than the exercise group. It did not beat liraglutide alone on weight, since the extra 2.7 kg was not statistically significant. The combination did reduce body fat by 3.9 percentage points, about double the drop in either single group, and only the combination improved blood sugar control, insulin sensitivity and fitness. Liraglutide is an older GLP-1 medicine than semaglutide or tirzepatide, so these results may not carry over exactly.

A 2026 review of semaglutide and tirzepatide studies found that lean mass loss is generally proportional to the amount of weight lost, and that it should not be treated as a direct measure of muscle loss. It also found that data on strength and physical performance, especially in older adults, are limited. A second 2026 review proposed a protein target and progressive resistance training as part of care, which is a proposal and not a trial result.

A trial built to answer the question is under way. The LEAN-PREP study in Kuwait plans to randomize 232 adults starting semaglutide or tirzepatide to usual care, home-based resistance exercise three times a week, a higher-protein diet, or both, for six months. Its main measure is the size of a thigh muscle on MRI. The Atlas found only the published plan, not results.

Expert guidance

What experts say about exercise with a GLP-1 medicine

The 2025 advisory from four U.S. nutrition and obesity societies says structured strength training, or a mix of strength and aerobic work, is well established to help preserve lean mass during weight loss. It says aerobic activity alone has a smaller effect on keeping lean mass during rapid weight loss.

It also points to retrospective studies of people on GLP-1 medicines that support structured exercise, including one example of 360 minutes a week with an emphasis on strength work. That is a description of what was studied, not a target for you to hit. For the year-long liraglutide trial above, the advisory reports that exercise plus the medicine preserved bone density, while the medicine alone lowered it.

For general health, the World Health Organization recommends at least 150 minutes of moderate physical activity per week and says muscle strengthening benefits everyone. Those are general adult guidelines, not advice tailored to someone on a GLP-1 medicine. Chapter 9 of the beginner guide covers muscle in more detail.

Community experience

What people report

People using GLP-1 medicines talk a lot about lifting weights, and they often describe it as the thing they wish they had started on day one. The themes people commonly describe are a fear of losing muscle, starting with simple full-body routines at home or a gym, and walking as the everyday habit that is easiest to keep.

People also commonly mention low energy on dose-increase days, dizziness when they have not eaten or drunk enough, and feeling slow to recover when eating very little. Many describe pairing workouts with a protein-rich meal.

None of this was measured. People who are proud of their routine are more likely to post, and nobody checks how hard or often they train. It is here because the topic is everywhere, not because it proves a method works.

Who needs to be careful

  • Anyone with heart disease, chest pain or breathlessness, or who has not exercised in a long time, should check with a clinician first.
  • Anyone with diabetes who uses insulin or a sulfonylurea, since exercise and a smaller appetite can both lower blood sugar.
  • Older adults, people with joint or bone problems, and anyone dizzy or very tired from low food intake.

Questions to bring to a clinician or dietitian

  • What kind and amount of exercise is safe for me to start with?
  • Do my diabetes or blood pressure medicines need to change if I exercise more?
  • Is a physical therapist or trainer who knows my history worth seeing?
  • Should we check my muscle or bone health with a body scan?

What is still unknown

  • Which exact program best protects muscle for people on semaglutide or tirzepatide has not been tested to completion.
  • Whether the results seen with liraglutide apply to newer medicines is unclear.
  • How much strength training, and at what intensity, is the minimum that matters is unknown.
  • Long-term results, such as whether the muscle kept lasts after stopping a medicine, are not well studied.

Related pages

Back to eating and exercise

Sources

  1. Healthy weight loss maintenance with exercise, liraglutide, or both combined Lundgren JR, et al. N Engl J Med. 2021;384(18):1719-1730. PMID 33951361. Funding: Novo Nordisk Foundation and others. Journal article
  2. Beyond weight loss: skeletal muscle health during incretin-based therapy in patients with diabesity Mollero ELM, et al. Nutrients. 2026;18(16). PMID 42654234. Funding: Not stated in the abstract. Journal article
  3. Medical nutrition in the GLP-1 era: protein strategies, micronutrient monitoring, and lean mass preservation Arslan S. Clin Nutr ESPEN. 2026;73:103305. PMID 42036071. Funding: Not stated in the abstract. Journal article
  4. LEAN mass Preservation with Resistance Exercise and Protein during semaglutide and tirzepatide therapy (LEAN-PREP study): a protocol for a randomised controlled trial Alawadhi AA, et al. BMJ Open. 2026;16(4):e116911. PMID 42020128. Funding: Not stated in the abstract. Journal article
  5. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and the Obesity Society Mozaffarian D, et al. Obes Pillars. 2025;15:100181. PMID 40673264. Funding: Professional societies; several authors report industry relationships. Journal article
  6. WHO fact sheet: Physical activity World Health Organization. Page dated 26 June 2024. Regulator