Sarcopenia—defined as the loss of skeletal muscle mass and function—is now recognized as a major complication and prognostic factor in chronic liver disease (CLD), including NAFLD, alcoholic liver disease, and cirrhosis. Current evidence indicates that altered protein metabolism, systemic inflammation, reduced dietary intake, and impaired ammonia detoxification accelerate muscle wasting in liver disease. Sarcopenia is strongly associated with increased morbidity and mortality among cirrhotic patients. Objective: To summarize contemporary evidence on the bidirectional relationship between sarcopenia and chronic liver disease progression, and to evaluate the impact of dietary protein intake and protein quality—including high-biological-value proteins and BCAA supplementation—on muscle preservation and clinical outcomes in CLD patients.

A focused literature search was conducted through PubMed and Google Scholar, including randomized controlled trials, cohort studies, and meta-analyses assessing sarcopenia prevalence, prognostic significance, and the effects of protein-based nutritional interventions in CLD. Mechanistic studies describing ammonia metabolism, muscle protein synthesis, and inflammatory pathways were also included.

• Sarcopenia affects approximately 30–70% of patients with cirrhosis and is independently associated with higher risk of infection, hepatic encephalopathy, portal hypertension complications, and increased mortality. • Protein intake below 1.0 g/kg/day is linked to accelerated muscle loss, while current guidelines recommend 1.2–1.5 g/kg/day to maintain or restore muscle mass in CLD. Supplementation with branched-chain amino acids (BCAAs) improves muscle protein synthesis, reduces ammonia levels, and enhances event-free survival in sarcopenic cirrhotic patients. • Evidence suggests that whey protein, BCAA-rich formulas, and high-quality plant proteins (e.g., soy) may support muscle preservation without increasing the risk of hepatic encephalopathy when total daily protein targets are met. • Sarcopenia contributes to liver disease progression by reducing metabolic reserve, increasing systemic inflammation, impairing immune function, and worsening clinical decompensation—indicating a bidirectional cycle between muscle loss and hepatic dysfunction.

Sarcopenia is both a consequence and a driver of chronic liver disease progression. Adequate dietary protein intake—supported by targeted supplementation such as BCAAs or high-biological-value proteins—plays a crucial role in preserving muscle mass, improving clinical outcomes, and potentially slowing the evolution of liver disease. Further high-quality randomized controlled trials are needed to determine optimal protein type, dose, and timing across different stages of chronic liver disease.