Sarcopenia and Frailty in COPD: Mechanisms, Relationship with Malnutrition and Potential Therapeutic Interventions

Background: Sarcopenia and frailty are highly prevalent extrapulmonary manifestations of chronic obstructive pulmonary disease (COPD) and are strongly associated with reduced exercise tolerance, exacerbation risk, hospitalizations, and mortality. Beyond inflammation, oxidative stress, and physical inactivity, emerging evidence highlights nutrition as a major modifiable driver of muscle deterioration in COPD. Nutritional deficits impair anabolic signaling, exacerbate proteolysis, worsen mitochondrial dysfunction, and contribute to frailty progression. Methods: This narrative review synthesizes evidence from PubMed, Embase, Scopus, and Web of Science up to 2025, integrating mechanistic, metabolic, nutritional, and biomarker-related pathways underlying muscle dysfunction in COPD. Studies examining inflammation, hypoxemia, oxidative stress, hormonal imbalance, nutrition, and emerging biomarkers were included. Results: COPD-related sarcopenia results from converging inflammatory (TNF-α, IL-6), catabolic (FOXO, UPS), metabolic, and vascular mechanisms, compounded by energy deficiency, protein insufficiency, and micronutrient deficits. Inadequate intake of protein, vitamin D, antioxidants, and omega-3 fatty acids increase anabolic resistance, enhance muscle catabolism, and worsen frailty. Nutritional interventions, particularly high-protein supplementation, leucine-enriched formulas, vitamin D repletion, omega-3 fatty acids, and multimodal nutrition–exercise programs, demonstrate benefits in muscle mass, strength, and physical performance. Biomarkers such as GDF-15, CAF22, and specific microRNAs reflect nutritional status and correlate with muscle health in COPD. Conclusions: Sarcopenia and frailty in COPD arise from a complex interplay of inflammatory, metabolic, nutritional, and lifestyle-related factors. Integrating nutritional assessment and targeted dietary interventions with exercise and pulmonary rehabilitation is essential to counteract anabolic resistance and improve functional outcomes. Advances in biomarker research may support earlier diagnosis and personalized nutrition-based therapeutic strategies.