According to LADbible, researchers at the University of the Fraser Valley, in collaboration with Les Mills and UKactive, reviewed data from users of several GLP-1 medications.
They found that participants tended to lose not only fat but also a meaningful portion of muscle mass.
The decline roughly matches what is typically seen over a decade of age-related muscle loss.
The review notes that muscle mass is crucial for mobility, metabolic health and overall resilience.
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Older adults may be especially vulnerable, as age already contributes to gradual weakening. Reduced muscle levels could increase the risk of falls and frailty.
Researchers added that structured exercise, particularly strength training, appears to help preserve lean mass during treatment.
Industry response
LADbible reports that Novo Nordisk, maker of Ozempic and Wegovy, emphasised that prescriptions should be made in consultation with healthcare professionals.
The company pointed to STEP 1 trial data showing decreases in both fat and muscle, with a larger reduction in fat.
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Eli Lilly, producer of Mounjaro, told LADbible that patient safety remains its priority and stressed the importance of diet, physical activity and medical follow-up, especially when users experience side effects.
Sources: LADbible, and Les Mills and UKactive.