Losing muscle while you lose weight is a big health concern on GLP-1 medication, and it is one you can do something about. Some of the weight you lose on this type of medication is muscle rather than fat, and maintaining it changes how strong you feel, how you look, and how well the weight stays off.
This article is about the why and the how of maintaining and building muscle. For the actual routine, with sets and reps, see our GLP-1 workout guide, and you can see our coached approach on our glp 1 exercise program.
Why do you lose muscle on GLP-1 medication?
You lose muscle on GLP-1 medication because when your body doesn’t get enough energy from food, it tries to save energy and may use some of your muscle for fuel as well as body fat.
When your appetite drops and less energy comes in, your body does not only burn fat. It sheds lean tissue too, including muscle. This is not unique to the medication; it happens with most large or rapid weight loss. But because GLP-1 medication reduces appetite so sharply, you can end up eating far less without really noticing. This increases the likelihood you will be eating insufficient protein which in turn reduces the body’s ability to repair and maintain muscle, consequently causing a reduction in muscle mass. The good news is that this is not inevitable, and the rest of this article is about how to prevent it.
How much muscle do you lose on GLP-1?
Research suggests around a quarter of the total weight people lose on GLP-1 medication can be lean muscle rather than fat (Karakasis et al., Metabolism, 2025).
That is the part the scales hide. If you step on and see you have lost ten kilos, you will quite rightly be pleased, but the scales cannot tell you how much of that was fat and how much was muscle. So the number going down is not the whole story, and being aware of that is the first step to doing something about it.
Why does losing muscle matter?
Losing muscle matters because it lowers your resting metabolism and makes the weight easier to regain.
Muscle is more metabolically active than fat, which means it burns more energy even when you are sitting still. Lose muscle and your body needs fewer calories, so your resting metabolism drops and weight can creep back more easily. There may be a second problem too. There is a proposal that after you lose muscle, the body drives you to eat more until it has been rebuilt, an effect called collateral fattening (Dulloo, Obesity, 2017). I call the pull back towards your old weight the Rebound Effect.
There is a longer-term reason as well. Muscle supports your strength, your mobility and your independence as you age, and we tend to lose it naturally over the years anyway. As Dr Gabrielle Lyon puts it in her book Forever Strong, many of us are "not over fat" but "under-muscled." So protecting muscle is not just about keeping weight off. It is about ending up stronger, not just lighter.
How do you know if you are losing muscle?
You can tell whether you are protecting muscle by watching your strength, not just the scales.
The scales will not show you the difference between fat and muscle, so they are a poor guide on their own. A better one is what your body can actually do. Are you as strong this month as you were last month performing certain resistance training exercises? Can you carry the shopping, climb the stairs or get up from a chair as easily as before, or more easily? If your strength is holding steady or improving while you lose weight, that is a good sign you are losing the right kind of weight. Body-composition measurements can help if you want them, but do not get too hung up on their exact accuracy. A positive way of measuring your muscle mass is to set a strength goal and consistently track it.
How do you preserve muscle while losing fat on GLP-1?
You preserve muscle on GLP-1 medication with two things working together: meeting protein requirements and regular resistance training.
Think of it as a reason and the raw materials. Resistance training gives your body a reason to hold on to muscle, because it signals that the muscle is still needed (Weinheimer, Sands and Campbell, Nutrition Reviews, 2010; Cava, Yeat and Mittendorfer, Advances in Nutrition, 2017). Protein provides the raw materials to maintain and rebuild it. You need both. Protein without training, or training without protein, will not be as effective.
Two practical points. First, start during your weight loss, not after it. The muscle you protect while the weight is coming off is far easier to keep than muscle you try to rebuild later. Second, put protein first at every meal. A recommended range is 1.2 to 2.0 grams of protein per kilogram of body weight a day for an active adult (Hickson et al., 2026), which for a woman weighing 60 kilograms is roughly 75 to 120 grams, but exact protein requirements do differ person to person. Resistance training does not mean a gym either. Your own body weight, resistance bands, and chair-based movements all count. For the step-by-step routine, see our GLP-1 workout guide.
Does preserving muscle need a coach?
Maintaining muscle is simpler with coached support that keeps the protein intake and the training on track.
None of this is overly complicated in theory. The hard part is doing it consistently when your appetite is low and life is busy, which is where many people slip. This is where support helps. A coach can personalise your protein goal to your personal needs, build a strength plan that actually fits your week, and keep you accountable so the two sessions a week really happen rather than drifting.
Rebecca, an illustrative example from my book, is a good example. A few weeks into her treatment she was delighted with the weight she had lost, but her muscle was dropping and she was feeling weaker. With her coach she tackled it from both ends at once, adding protein at every meal and booking regular strength sessions, and her strength came back. That combination of nutrition and training, managed alongside the medication, is exactly what our coached programme is built around. Speak to your prescriber and coach about the right plan for you, and remember results vary from person to person.
Simon Hill is Chief Executive of GLP-1 company Mission MNT, founder of the Hartfield Healthcare Group and author of The Rebound Effect, published by Rethink Press in January 2027, on why weight loss on GLP-1 medication so often doesn't last and what actually keeps it off.
Dietetically reviewed by Callum Jones (HCPC DT035272). Registered Dietitian with a Foundation Degree in Sport Development, BSc in Nutrition and PG Diploma in Dietetics, complemented by qualifications in Personal Training and Exercise Referral. Brings experience working within professional rugby, combining clinical dietetic expertise with practical exercise and training experience. Provides an integrated approach to nutrition, weight management, physical activity and long-term health, supporting individuals to make sustainable lifestyle changes.
Published: 08.10.2026 Next review: 08.10.2027
Sources
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Karakasis, P., Patoulias, D., Fragakis, N. and Mantzoros, C.S. (2025) 'Effect of glucagon-like peptide-1 receptor agonists and co-agonists on body composition: systematic review and network meta-analysis', Metabolism: Clinical and Experimental, 164, 156113. doi:10.1016/j.metabol.2024.156113.
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Dulloo, A.G. (2017) 'Collateral fattening: when a deficit in lean body mass drives overeating', Obesity, 25(2), pp. 277-279.
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Weinheimer, E.M., Sands, L.P. and Campbell, W.W. (2010) Nutrition Reviews. (Full details to confirm from the manuscript reference list.)
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Cava, E., Yeat, N.C. and Mittendorfer, B. (2017) Advances in Nutrition. (Full details to confirm.)
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Hickson, M., Maslin, K., Wedlake, L., Mellor, D. and Brown, A. (eds.) (2026) Manual of Dietetic Practice. 7th edn. Hoboken, NJ: Wiley
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Mozaffarian, D. et al. (2025) Obesity. (Full details to confirm.)
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Bauer, J. et al. (2013) Journal of the American Medical Directors Association. (Protein intake range; full details to confirm.)
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Lyon, G. (2023) Forever Strong.
DISCLAIMER: This article was produced in part using generative AI with clinical review and sign-off. The information provided in this article is intended for general informational purposes only and should not be construed as medical advice, diagnosis, or treatment. The products and methods mentioned are not a substitute for professional medical advice from a trained healthcare specialist. Always seek the guidance of your doctor or other qualified health professional with any questions you may have regarding your health or a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. Use of the information and products discussed is at your own risk.
Registered Dietitian with a Foundation Degree in Sport Development, BSc in Nutrition and PG Diploma in Dietetics, complemented by qualifications in Personal Training and Exercise Referral. Brings experience working within professional rugby, combining clinical dietetic expertise with practical exercise and training experience.
Provides an integrated approach to nutrition, weight management, physical activity and long-term health, supporting individuals to make sustainable lifestyle changes.
HCPC Registration: DT035272
