Sarcopenia in type 2 diabetes mellitus: from muscle quantity to multidimensional muscle health.

Type 2 diabetes mellitus (T2DM) is increasingly recognized as a condition in which skeletal muscle impairment extends beyond loss of muscle mass alone. Epidemiologic evidence indicates that sarcopenia is more common in individuals with T2DM and is associated with mortality, cardiovascular disease, and diabetes-related complications. Recent research has therefore shifted toward a multidimensional view of muscle health that incorporates muscle strength, physical performance, muscle composition, myosteatosis, muscle density, and strength relative to muscle mass. This review synthesizes the epidemiology, clinical significance, diagnostic frameworks, and pathophysiological basis of sarcopenia in T2DM, with particular attention to the relationships among muscle mass, strength, composition, and function. It evaluates emerging evidence on myosteatosis, multimodal muscle assessment, continuous glucose monitoring-derived glycemic phenotypes, sarcopenic obesity, and contemporary glucose-lowering and weight-loss therapies. Current evidence remains limited by heterogeneous sarcopenia definitions, muscle-mass normalization methods, and measurement techniques, while studies of myosteatosis, glycemic variability, and emerging biomarkers are still predominantly observational. In addition, trials of potent glucose-lowering and weight-loss therapies commonly emphasize body weight, lean mass, or muscle volume rather than integrated muscle-centered outcomes. A more coherent framework that jointly evaluates muscle quantity, composition, strength, and physical performance is needed to improve early detection, risk stratification, and intervention research in diabetes-related muscle health.