Nutritional and Metabolic Interventions to Prevent and Treat Protein–Energy Wasting in Nondialysis CKD—Narrative Review

Background: Protein–energy wasting (PEW) is a major predictor of morbidity and mortality in patients with chronic kidney disease (CKD), even before the initiation of dialysis. Its multifactorial pathogenesis includes reduced dietary intake, chronic inflammation, metabolic acidosis, hormonal disturbances, and dysbiosis of the gut microbiota. Early recognition and targeted management are crucial for preventing muscle loss, functional decline, and adverse outcomes. Methods: This narrative review summarises and integrates current evidence from the literature on nutritional and metabolic interventions to prevent and treat protein–energy wasting in patients with nondialysis chronic kidney disease. Relevant clinical trials, meta-analyses, and experimental studies published up to date were evaluated, focusing on dietary strategies, metabolic modulation, physical exercise, and gut microbiome-targeted therapies. Results: Adequate energy and protein intake remain the cornerstone of PEW management, based on available clinical and observational evidence. Individualised diets emphasising high-quality and plant-based proteins, oral nutritional supplements, and ketoanalogues can attenuate muscle wasting. Correction of metabolic acidosis and inflammation enhances protein anabolism and nitrogen balance. Physical exercise acts synergistically with dietary interventions to preserve muscle mass and function. Novel approaches—such as modulating the gut–kidney axis with pre-, pro-, and postbiotics or supplementing with short-chain fatty acids—show promise in improving metabolic and inflammatory profiles. Conclusions: The management of PEW in nondialysis CKD requires a personalised approach that integrates nutrition, physical activity, metabolic correction and microbiome modulation. Early, coordinated intervention may help to slow the progression of CKD and improve patient survival and quality of life.