Protein and Muscle Health During GLP-1 Treatment

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Protein-Smart Eating During GLP-1 Weight Loss

A physician-led educational guide to help you understand protein, nutrition and muscle health during treatment.

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What the evidence shows

What Happens to Your Body During Weight Loss

When people lose a significant amount of weight — through any method — the weight that comes off is not made up of fat alone. Some lean tissue is lost as well. This is a normal part of weight loss, and the proportion lost as lean tissue during treatment with these medicines is broadly similar to other substantial weight-loss approaches.^1,3

In studies of incretin-based treatments, most of the weight people lost was fat.^1,3

Lean mass is not the same thing as muscle

You may see the term "lean mass" used in articles about weight loss. It is worth understanding what it actually means.

Lean mass is everything in the body that is not fat. That includes skeletal muscle — the muscle you use to stand, lift and walk — but it also includes water, organs and connective tissue. Body-composition scans do not measure skeletal muscle directly; they estimate it, and part of a reported change can reflect shifts in body water rather than a loss of muscle itself.⁹

This matters because a falling number on a scan is not, by itself, evidence that a person has lost strength or function.^2,3,9

What the evidence does and does not show

Researchers are still working out how much of the lean tissue change during incretin treatment represents skeletal muscle, and what it means for how people actually feel and move. The available evidence does not establish that these medicines cause a disproportionate loss of muscle.^1,3

Measures that matter to daily life — strength, walking, getting out of a chair, carrying shopping — have been studied less often in these trials than weight and scan results have. Where strength has been measured, it did not decline.^1,2,3

The goal is not to protect a number on a scan. The goal is to come through weight loss strong, well-nourished and able to do the things you need to do.

Eating during treatment

Why Eating Enough Can Become Harder

These medicines work in part by reducing appetite. That is the point of the treatment, and for many people it is exactly what helps. But the same effect can make it genuinely harder to eat well — and that is a practical problem worth planning for rather than a sign that something has gone wrong.

What people may notice

• Feeling full much sooner than expected
• Little or no appetite at usual mealtimes
• Nausea, particularly in the early weeks or after a dose increase
• Food losing its appeal
• Meals becoming smaller without any deliberate decision

These effects are well described in studies of these medicines.^2,8

None of this means you are undernourished. It does mean that eating well now takes more thought than it did before — because the appetite signals that used to organise your eating are quieter.

When to contact your clinician

Some symptoms need clinical attention rather than self-management. Contact your clinician if you experience:

Do not change how you take your medicine on your own. If symptoms are making treatment difficult, that is a conversation to have with the clinician who prescribed it.

Before you change what you eat

Before You Change What You Eat — A Safety Checkpoint

Please read this page before acting on anything that follows.

The rest of this guide describes practical ways to include protein in everyday eating. Before you increase your protein intake substantially, there is something important to understand.

Protein needs are not the same for everyone

There is no single protein amount that is right for every person. What is appropriate depends on your health, your medical conditions, your nutritional state, your activity and your treatment. Two people the same age and weight can genuinely need different amounts.^6,7

Speak with your clinician first if any of these apply to you

• You have kidney disease, reduced kidney function, or have been told to watch your kidneys
• You are on dialysis, or have had a kidney transplant
• You have been given a specific diet by a clinician or dietitian
• You have another medical condition for which you have been given specific dietary advice
• You are unsure whether any of the above applies to you

An important point about kidney health

People sometimes assume that kidney disease automatically means eating less protein. That is not accurate, and acting on that assumption can be harmful.

Protein guidance in kidney disease depends on several things — including the stage of the condition, whether someone is on dialysis, their nutritional state, and whether they are frail or losing muscle. In some situations clinicians advise reducing protein. In others — including dialysis, and in some older adults who are frail or have low muscle — clinicians advise the opposite.^6,7

This is exactly why it is a conversation with your own clinician rather than something to work out from a guide. Your clinician knows your kidney function, your history and your nutrition. A booklet does not.

About MyoGuard

MyoGuard Protocol is a physician-led Clinical Decision Support platform, designed to be used by clinicians alongside their own judgement when caring for people on GLP-1 and related treatments.

The Sarcopenia Risk Index (SRI) is a physician-led Clinical Decision Support tool that helps clinicians consider factors associated with vulnerability to sarcopenia and muscle compromise during treatment.

It is not a diagnosis. It does not predict what will happen to any individual. It supports clinical judgement rather than replacing it, and every output is interpreted by the treating clinician.

Important

This guide is general education. It is not medical advice, it is not a diet plan, and it does not create a clinician–patient relationship. Decisions about your treatment, your diet and your health belong with you and your own clinician.

References

1. Look M, Dunn JP, Kushner RF, et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study. Diabetes Obes Metab. 2025;27(5):2720-2729. DOI 10.1111/dom.16275. PMID 39996356.
2. Alissou M, et al. Impact of semaglutide on fat mass, lean mass and muscle function: the SEMALEAN study. Diabetes Obes Metab. 2026;28(1):112-121. DOI 10.1111/dom.70141. PMID 41068996.
3. Laverde LP, Muñoz-Velandia OM, Alfonso D, Gómez Medina AM. Effect of GLP-1 receptor agonists at doses for obesity management on muscle health. Int J Obes. 2026;50(8):1638-1646. DOI 10.1038/s41366-026-02118-y. PMID 42321502.
4. Verreijen AM, Engberink MF, Memelink RG, et al. Nutr J. 2017;16:10. DOI 10.1186/s12937-017-0229-6. PMID 28166780.
5. Villareal DT, Aguirre L, Gurney AB, et al. N Engl J Med. 2017;376(20):1943-1955. DOI 10.1056/NEJMoa1616338. PMID 28514618.
6. Bauer J, Biolo G, Cederholm T, et al. PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-559. DOI 10.1016/j.jamda.2013.05.021.
7. KDIGO CKD Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117-S314. DOI 10.1016/j.kint.2023.10.018.
8. Karrar HR, et al. Tirzepatide-induced gastrointestinal manifestations: a systematic review and meta-analysis. Cureus. 2023;15(9):e46091. DOI 10.7759/cureus.46091. PMID 37908927.
9. Baglietto N, Vaquero-Cristóbal R, Albaladejo-Saura M, et al. Front Nutr. 2024;11:1445892. DOI 10.3389/fnut.2024.1445892. PMID 39224178.