Peter Attia prescribes GLP-1 agonists clinically and flagged the lean mass loss problem early: 39% of weight lost in the STEP 1 trial was lean tissue. His protocol follows standard FDA titration (0.25mg to 1mg+ weekly) but pairs it with resistance training and 1g protein per pound of bodyweight. This is a prescriber's perspective, not personal biohacking. DEXA scans and metabolic panels required.