As millions turn to GLP-1 medications for weight management, a quieter reckoning is underway: the body, losing weight rapidly, does not discriminate between fat and muscle. Experts across medicine and exercise science are now framing strength training not as a lifestyle supplement but as a clinical necessity — a way of telling the body, in the language of effort and resistance, that its lean tissue is worth keeping. The lesson embedded in this guidance is an old one: transformation without preservation is not always progress.