Sarcopenia in Hospitalized Patients: A Critical Narrative Review of Diagnostic and Nutritional Management Approaches

Sarcopenia is an independent predictor of adverse outcomes in hospitalized patients, associated with increased mortality, prolonged length of stay, and functional decline, yet it remains underdiagnosed owing to inconsistent diagnostic criteria and the practical challenges of assessing acutely ill patients. This narrative review summarizes current evidence on sarcopenia in hospitalized patients, with emphasis on diagnostic approaches, nutritional requirements, and optimal nutritional support strategies. Sarcopenia is particularly prevalent among critically ill patients and is driven by the convergence of systemic inflammation, immobility, and anabolic resistance. Diagnosis remains challenging: no ICU-specific framework exists, and the recent Global Leadership Initiative of Sarcopenia consensus established a unified, setting-independent conceptual definition as a foundation for future operational criteria, with ICU-specific frameworks yet to be developed. Bedside tools, including handgrip strength, bioelectrical impedance analysis, and ultrasound, retain strong prognostic value despite imperfect agreement with reference imaging. Nutritional intervention is a key component of management; however, large-scale trials have demonstrated that higher energy or protein delivery does not universally improve outcomes and may be harmful in selected critically ill patients. A gradual increase in energy and protein delivery according to the phase of illness, with protein targets of ≥1.2-1.5 g/kg/day, is recommended; leucine-enriched supplementation may help counteract anabolic resistance, although direct evidence in non-ICU hospitalized patients remains limited. Early mobilization is an essential complement, as nutrient provision without a mechanical stimulus cannot reverse immobility-induced muscle loss. A practical clinical algorithm integrating screening, nutritional target-setting, route selection, and reassessment is proposed to guide decision-making in this population. Future research should focus on improving the accuracy and feasibility of muscle assessment tools in critically ill patients to enable the timely diagnosis of sarcopenia and nutritional intervention, alongside the development of validated multi-marker panels and adequately powered trials examining the combined effect of nutrition and exercise in this population.