GLP1 medicines and muscle: the side of weight loss we need to talk about
GLP1 receptor agonists such as semaglutide have transformed weight management. As prescribing grows, including through telehealth and longevity services, a quieter question is getting louder: what happens to muscle?
How much of the weight lost is muscle?
A 2025 review in Acta Diabetologica found that roughly 25% to 30% of total weight lost on GLP1 medicines is lean tissue (Rossi et al., Acta Diabetologica, 2025). The authors note this is similar to weight loss by diet alone, and that mobility and function are generally maintained in the studies so far.
That is reassuring for many people. It is less reassuring for older adults.
Why age changes the picture
The same review highlights that older users appear to lose a greater proportion of lean mass than younger adults. Older muscle also responds less to protein and exercise, a phenomenon known as anabolic resistance. For someone already close to the threshold for sarcopenia, losing muscle during weight loss can tip the balance towards weakness, falls and loss of independence.
What the review recommends
Resistance training, combined with moderate aerobic activity, throughout treatment.
Adequate protein, around 1.2 to 1.6 g per kilogram of adjusted body weight each day, spread across meals.
Monitoring function, such as grip strength and walking speed, alongside body composition where available.
The opportunity for clinicians and platforms
GLP1 prescribing often happens quickly and remotely. The exercise side of the prescription rarely does. That is a gap allied health can fill, and one that platforms prescribing these medicines should plan for from day one.
A structured, supervised strength program delivered to the patient's phone, with a clinician able to see that sessions are happening, is a practical way to protect muscle while the scales go down.
This article is general information for health professionals and is not clinical advice. Decisions about GLP1 medicines should be made with the prescribing doctor.
