Cancer cachexia describes the muscle wasting and weakness that robs many patients with cancer of their strength and capacity to perform daily tasks and to live independently. Activation of the mitochondrial assembly receptor (MasR) had multiple benefits for tumor-bearing mice with cancer cachexia, including attenuated tumor development, reduced weight loss, slowed muscle wasting, and improved locomotor activity. MasR-mediated protection against muscle wasting was conferred through preservation of the large, fast muscle fibers. For details, see article by Murphy and colleagues on page 706.