Let's get right into it: How much of the weight people are losing on GLPs is coming from muscle and not fat? Some of the research and clinical data is staggering. In the landmark trials: - Semaglutide (STEP-1): ~15% body-weight loss over 68 weeks, with roughly 40% of that loss coming from lean mass. - Tirzepatide (SURMOUNT-1): ~21% body-weight loss, with about 25% from lean mass — a more favorable ratio. Because tirzepatide drives larger total loss, the absolute pounds of muscle at risk can be similar or higher, and newer real-world (routine-care) data in 2026 actually found greater relative lean-mass loss on tirzepatide than semaglutide over 12 months. Translation: don't assume the "better" drug protects your muscle for you. Neither does. You do. On the positive though: in studies where people paired their GLP-1 with enough protein and resistance training, lean-mass loss dropped to nearly nothing, on the order of 1–2 lbs total.. Why it happens (the mechanism, briefly) GLP-1 medications are appetite silencers. They mimic your gut's own glucagon-like peptide-1, slow gastric emptying, and blunt ghrelin, the "I'm hungry" hormone. You simply eat less, often dramatically less. The 3-part muscle-preservation playbook: 1. Hit a real protein floor every single day. The evidence target for preserving lean mass during weight loss is at least ~1.6 g of protein per kg of body weight per day. On a GLP-1, where appetite is suppressed, the practical rule is simpler: never drop below ~100 g of protein a day, and aim higher. For most people that looks like 2 protein-anchored meals of ~40–50 g each, topped up with a whey or essential-amino-acid (EAA) shake. Protein is also the most satiating macro, so this is the easiest one to defend even on a tiny appetite. 2. Front-load leucine (whey + EAAs are your friends). It's not just total protein — it's getting enough leucine per meal to actually trigger muscle-protein synthesis. Whey protein and EAA supplements are the most reliable, muscle-preserving way to do this when whole-food appetite is low. One or two servings a day covers most people who are struggling to eat.