Circadian Rhythms, Exercise, and Metabolic Remodeling in MASLD: From Chronometabolism to Muscle-Preserving Care

Metabolic dysfunction-associated steatotic liver disease (MASLD) links hepatic lipid accumulation with insulin resistance, disturbed sleep, and impaired muscle health. This critical narrative review integrates clinical, metabolomics, and mechanistic evidence identified through a structured multi-database search and citation-tracing workflow covering PubMed, Web of Science, Scopus, and Google Scholar to 30 September 2026, focusing on circadian regulation, exercise, and muscle-preserving care. Hepatic clocks coordinate nutrient handling, bile-acid signaling, mitochondrial metabolism, and redox balance. Sleep and meal-timing disruption are associated with adverse metabolic phenotypes, although MASLD-specific causal evidence remains limited. Exercise improves liver and metabolic outcomes, but no universal optimal session time has been established. Time-restricted eating should be evaluated alongside energy intake, diet quality, protein distribution, sleep, and adherence. Complex lipids, acylcarnitines, bile acids, ketone bodies, and amino acids offer complementary research signals; their interpretation requires standardized sampling, analytical quality control, and external validation. Circulating concentrations should not be equated with tissue flux or treatment benefit. Clinical care should integrate fibrosis and cardiometabolic risk assessment with sustainable weight management, progressive resistance and aerobic exercise, adequate protein, and sleep assessment. Future trials should pair repeated, timed metabolite measurements with liver, body-composition, strength, and physical-function outcomes to establish whether these signatures improve clinical decisions.