Mixed
GLP-1-based therapies (semaglutide, tirzepatide) cause lean mass loss proportional to total weight loss (approx. 15-45%), but this reduction is adaptive and accompanied by improved muscle quality (reduced fat infiltration), resulting in preserved or improved muscle function and strength.
If you are taking a GLP-1 medication like semaglutide or tirzepatide, expect to lose some muscle along with fat. This is normal and proportional to your weight loss. Crucially, these drugs often improve muscle quality by reducing fat inside the muscle, which helps preserve your strength and function. To maximize muscle retention, ensure you are consuming adequate protein and engaging in resistance training if possible.
skeletal muscle changes with GLP-1RA treatments appear to be adaptive: reductions in muscle volume seem to be commensurate with what is expected given ageing, disease status, and weight loss achieved, and the improvement in insulin sensitivity and muscle fat infiltration likely contributes to an adaptive process with improved muscle quality, lowering the probability for loss in strength and function.
Why this rating
Based on multiple RCTs (STEP-1, SURMOUNT-1, SUSTAIN-8) and MRI studies, though heterogeneity exists.
Source
Changes in lean body mass with <scp>glucagon‐like peptide</scp> ‐1‐based therapies and mitigation strategies
Ian J. Neeland et al. · Diabetes Obesity and Metabolism · 2024
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