Tirzepatide vs Semaglutide Muscle Preservation: Which Preserves More Lean Mass?
GLP-1 & Obesity Medicine Guide • Updated October 7, 2026 Semaglutide and tirzepatide can produce substantial weight loss, but an important question follows: How much of the weight lost is fat, and how much is lean mass? The question is more complicated than it first appears. Studies of semaglutide and tirzepatide show that both treatments reduce fat mass and can also reduce lean mass during weight loss. But lean mass is not synonymous with skeletal muscle , and results from separate trials cannot be treated as a direct head-to-head comparison of muscle preservation. A 2026 systematic review and meta-analysis of 20 randomized controlled trials involving 15,782 participants estimated that lean mass represented approximately 35.2% of weight lost with semaglutide and 25.4% with tirzepatide . The analysis also found a more favorable proportion with lifestyle intervention that incorporated r...