Docs Who Lift Do You Really Lose Muscle on Semaglutide or Tirzepatide?
Aug 22, 2025
In this discussion, body composition expert Grant Tinsley shares valuable insights on GLP-1 receptor agonists like semaglutide and tirzepatide. He highlights the remarkable body composition changes observed in patients, illustrating how one lost significant fat while preserving lean mass. The importance of resistance training and proper nutrition in weight management takes center stage. Tinsley emphasizes the need for more randomized trials to deepen understanding, all while underscoring individual experiences with these innovative weight loss treatments.
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Objective DEXA Data Reduces Confounders
- The case series used serial DEXA scans from a single facility to reduce measurement error.
- Grant Tinsley reviewed reports and presented raw participant data to show real-world variability.
Average Lean Loss Masks Individual Variation
- Reported lean soft tissue loss across GLP-1/dual agonist trials ranged roughly 26–40% of total weight loss.
- Individual responses vary widely, so averages can mislead for specific patients.
Longcase: Big Fat Loss, Minimal Lean Loss
- A 42-year-old woman on tirzepatide trained ~3 days/week and did mixed cardio and resistance exercise.
- Over 115 weeks she lost 33% body mass and only ~9% of weight loss was lean soft tissue.