The Muscle Loss Problem with GLP-1s
Clinical data consistently shows that 25-40% of weight lost on GLP-1 monotherapy comes from lean mass (muscle and bone), not just fat. This is catastrophic for long-term metabolic health—less muscle means lower basal metabolic rate, meaning weight regain becomes almost inevitable after cessation.
The STEP trials revealed that semaglutide users lost approximately 39% lean mass as a proportion of total weight lost. Tirzepatide shows marginally better muscle preservation (~25-30% lean mass loss).
Preservation Strategies
Protein intake of 1.2-1.6 grams per kilogram of body weight daily is the single most protective factor. At the reduced appetites GLP-1s create, protein must be prioritized at every meal.
Resistance training 3-4 times weekly with progressive overload provides the mechanical loading stimulus that signals the body to preserve existing muscle during caloric deficit.
Creatine monohydrate (5g/day) supports intramuscular energy during training. Some researchers combine GLP-1s with low-dose testosterone or GHRP-6 to offset the catabolic environment.