GLP-1 drugs like Ozempic cause muscle loss during weight reduction, but newer research reveals DEXA scans misrepresent true muscle loss, and strength often improves despite lean mass decline. Peter Attia examines how much muscle is actually lost, compares GLP-1s to other weight-loss methods, and outlines evidence-based strategies for preserving muscle and bone while using these medications. Early clinical trials showed near one-to-one lean mass to fat loss ratios on GLP-1 drugs (50% of weight loss from muscle), but newer research indicates DEXA measurements overestimate actual muscle loss due to intramuscular fat changes.