Longevity & AgingDoes Weight Loss From Semaglutide and Tirzepatide Cost You Muscle? A Systematic Review Weighs In
GLP-1–based drugs such as semaglutide and tirzepatide drive major weight loss, but clinicians worry some of it is muscle rather than fat. This systematic review examined 35 randomized trials of liraglutide, semaglutide, tirzepatide, or dulaglutide that measured body composition. People on incretin drugs consistently lost fat mass and visceral fat. However, muscle-related measures accounted for a median of 28.3% of total weight lost, and about two thirds of studies exceeded prespecified benchmarks for expected muscle loss. Lifestyle or placebo groups that lost weight also often exceeded the benchmarks, though they lost far less weight overall. No trial measured physical function, so whether these lean mass losses matter clinically remains unknown. The trials were short, small, and too varied to combine statistically.
