GLP-1 Weight Loss, Muscle Loss and Bone Health: What Movement Professionals Need to Know
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The weight is dropping off but is anything else?
Weight loss v muscle loss and the role of manual and movement therapists
The urgency regarding obesity and the health issues that surround it has been clear for some time.Stomach stapling and other surgical procedures are expensive invasive and carry significant risks and the long term results have been at best, mixed.
In more recent years, medications known as Glucagon Like Peptide - GLP-1s have changed the landscape when considering obesity.Used originally to control diabetes, the brand names such as Wegovy, Mounjaro and Ozempic have become almost household names, producing levels of weight loss that were previously difficult to achieve without surgery, while also improving several obesity-related health risks. (Kosiborod et al., 2023)
In spite of the degree of bullying it attracts, obesity is not some kind of a moral failure, but losing substantial weight where it exists can improve health, mobility and quality of life. The conflict often comes where people feel that the use of pharmaceutical treatment is an extension of the failure they already perceive.
Nothing could be further from being either truthful or helpful. If failures of morality exist anywhere they should fall on those responsible for the creating of mass produced, ultra processed foods that are easy to consume and cheap to produce. The lack of regulation around them and the enormous power wielded by huge corporations that produce them are issues that extend beyond the scope of this piece. But here we are with a problem, being offered an extremely helpful step towards solving it.
The benefits of these medications should not therefore be dismissed simply because pharmaceutical treatment makes some people uncomfortable.
However, weight loss and health improvement are not the same thing. When people lose a considerable amount of weight, they do not just simply lose fat and fat alone. Some lean body mass usually disappears with it, something that often isn’t made clear to those starting out taking them.
That also creates an important and largely overlooked role for personal trainers, Pilates teachers, movement professionals and hands-on therapists.
Lean mass: not just muscle
Headlines commonly make alarming statements that as much as a third of the weight lost on GLP-1 drugs is muscle, a claim that needs some degree of qualification. Most trials measure ‘lean mass’ using techniques such as DXA, a low dose X-ray scan that estimates bone mineral, fat mass and lean soft tissue in different parts of the body. Lean mass is everything that isn’t fat or bone mineral and includes muscle, organs, connective tissues, body water and other elements.
Therefore, measured like this, losing ‘lean mass’ doesn’t automatically translate into a loss of muscle but the concern is still worth noting.
In the original STEP 1 trial of semaglutide, (the active ingredient for Ozempic,) participants lost 15% of their body weight compared with 2.4% in the control group (Wilding et al., 2021). Most of the weight loss was fat but lean tissue mass also declined. (Conte et al., 2024) Studies for other drugs reveal the similar patterns. (Look et al., 2025).
This isn’t evidence that medications are having a destructive effect on muscle. Any large weight loss programs will do the same and calorie-restricted dieting and bariatric surgery have been shown to have the same effect on lean mass loss. (Weiss et al., 2018)
Someone whose appetite has been sharply reduced may consume less protein and less total energy. If that person also has no history of resistance training, the body has little reason to retain muscle tissue that has to be maintained by a metabolism.
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The people most in need may be least prepared
Although recommendations from prescribing physicians will tend to pair weight-loss medication with increased physical activity and dietary change, in reality those instructions may amount to vague instructions to, “eat well and exercise”.
Many people living with obesity don’t have an established relationship with exercise. Some have joint pain, breathlessness, balance problems or years of embarrassment associated with gyms. (Okifuji & Hare.,2015) Others may have repeatedly encountered fitness environments in which exercise was presented as punishment for eating or as a way of earning food. Simply handing someone a prescription and telling them to start resistance training doesn’t create the confidence, skill or knowledge required to do actually it.
This is where the fitness and movement sector can step in and be useful although attitudinal changes and a different offer might be required. The idea of exercise for weight loss is somewhat redundant in these instances, with the medication creating the energy deficit need for that to happen.
Instead, the goal becomes to support someone maintaining muscle tone and strength, loading bone and working towards new habits that include regular movement and resistance.
Bone is part of the picture
Weight loss can also affect bone. (Weiss et al., 2018) A lighter body places less load through the skeleton, while restricted food intake may reduce the consumption of protein, calcium, vitamin D and other nutrients needed for bone health.
This isn’t to say that everyone using a GLP-1 drug will develop osteoporosis, nor does it suggest that the medication somehow directly damages bone.
A Danish randomised trial followed 195 obese adults after an initial low-calorie diet. (Lundgren et al., 2021) Participants received exercise, liraglutide, (another weight loss medication) both interventions or placebo for a year. Liraglutide without exercise was associated with reductions in bone mineral density, while exercise helped preserve bone despite further weight loss. The combination of approaches produced considerable weight loss without the same bone loss. (Jensen et al., 2024).
Fatigue, exercise tolerance and injury
Nausea, vomiting, diarrhoea, constipation, dizziness and fatigue are all recognised experiences among some users of weight loss medications. Reduced food and fluid intake may also affect energy, hydration and tolerance to exercise.
However there doesn’t seem to be any convincing evidence that I have found, linking GLP-1 drugs to any kind of increase in exercise injuries. It could be that this a group or association that has yet to be studied, but the greater concern is more subtle.
Someone may have lost considerable weight without developing equivalent strength, balance or movement skill. They may feel more able to move because their body is lighter, while their tissues and nervous system remain unprepared for sudden increases in walking, running, lifting or recreational activity. Appearances can be deceptive and body weight is no real indicator of load capacity.
Starting points such as sit-to-stand movements and supported resistance movements are the safe options, but ultimately the specifics of the exercise matter less than the consistency of them.
A role for hands-on practitioners
The hands on therapist also has a huge role to play in supporting people in their weight loss journey.
Although massage therapists, Bowen practitioners and other hands-on professionals cannot manually prevent muscle loss or rebuild bone, their potential value exists in different spheres.
I have seen clients who certainly don’t regard themselves as exercisers and who although pleased with their progress are still reluctant to approach a gym or find trainer. This uncertainty about what comes next, means that for many they are yet to consider what might replace the medications and fear the weight going back on.
Alongside this are the reports of declining energy, the sensations around rapid physical change and other issues like sleep that sometimes manifest. (Krentz et al., 2016) A good manual therapy session with a therapist acquainted with the medications and the issues around them, can help clients to feel more confident in their bodies.
Offers of support around any aches that might be experienced with new kinds of movement and personal recommendations of trainers who have been similarly educated, allow for of people experiencing significant personal changes like weight loss. Providing informed support and creating a bridge towards appropriate exercise or healthcare is the pinnacle of therapeutic care.
A genuine professional opportunity
Whilst there is a definite business opportunity being presented, it should most definitely not be built around frightening people into believing their muscles are disappearing.
A responsible approach might provide a non-judgemental introduction to resistance training, gradual progression, balance work, exercise adapted around side effects and collaboration with other health providers where appropriate.
Many people using GLP-1 medication will need more than just an instruction to exercise. The injections are doing the heavy lifting as it were, but they will need someone who understands that becoming lighter doesn’t automatically make a person stronger, fitter or more physically confident.
Helping these clients to a better understanding their physical potential is where good manual and movement therapists can create value and service.
References
Conte, C. et al. (2024) ‘A systematic review of the effect of semaglutide on lean mass: insights from clinical trials’, Expert Opinion on Pharmacotherapy, 25(6), pp. 611–619. https://doi.org/10.1080/14656566.2024.2343092
Jensen, S.B.K. et al. (2024) ‘Bone health after exercise alone, glucagon-like peptide-1 receptor agonist treatment, or combination treatment: A secondary analysis of a randomised clinical trial’,JAMA Network Open, 7(6), e2416775.
Kosiborod, M.N. et al. (2023) ‘Semaglutide in patients with heart failure with preserved ejection fraction and obesity’, New England Journal of Medicine, 389, pp. 1069–1084. https://www.nejm.org/doi/full/10.1056/NEJMoa2306963
Krentz, A.J., Fujioka, K. and Hompesch, M. (2016), Evolution of pharmacological obesity treatments: focus on adverse side-effect profiles. Diabetes Obes Metab, 18: 558-570. https://doi.org/10.1111/dom.12657
Lundgren, J.R. et al. (2021) ‘Healthy weight loss maintenance with exercise, liraglutide, or both combined’, New England Journal of Medicine, 384, pp. 1719–1730. https://www.nejm.org/doi/full/10.1056/NEJMoa2028198
Look, M. et al. (2025) ‘Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study’,Diabetes, Obesity and Metabolism, 27(1), pp. 199–207. https://dom-pubs.onlinelibrary.wiley.com/doi/full/10.1111/dom.16275
Okifuji, A., & Hare, B. D. (2015). The association between chronic pain and obesity. Journal of Pain Research, 8, 399–408. https://doi.org/10.2147/JPR.S55598
Rubino, D. et al. (2021) ‘Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity’, JAMA, 325(14), pp. 1414–1425.
Weiss EP, Jordan RC, Frese EM, Albert SG, Villareal DT. Effects of Weight Loss on Lean Mass, Strength, Bone, and Aerobic Capacity. Med Sci Sports Exerc. 2017 Jan;49(1):206-217. doi: 10.1249/MSS.0000000000001074. PMID: 27580151; PMCID: PMC5161655.
Wilding, J.P.H. et al. (2021) ‘Once-weekly semaglutide in adults with overweight or obesity’, New England Journal of Medicine, 384, pp. 989–1002.https://www.nejm.org/doi/full/10.1056/NEJMoa2032183
