Abstract
Background: Pediatric obesity exemplifies the paradox of energy excess coexisting with nutritional inadequacy. Despite high caloric intake, children with obesity often display deficiencies in essential macro- and micronutrients that impair growth, metabolic regulation, and long-term health. This review critically examines the mechanisms underlying malnutrition in pediatric obesity, emphasizing the interplay between dietary quality, inflammation, microbiota alterations, and biomarker profiles, and identifies research gaps limiting precision nutrition approaches. Methods: A comprehensive narrative review of studies addressing macro- and micronutrient intake, metabolic and inflammatory biomarkers, and gut microbiota-host interactions in pediatric obesity was conducted. Evidence from both clinical and experimental models was integrated to evaluate mechanistic pathways, diagnostic criteria, and preventive strategies. Results: Obesity-related malnutrition arises from poor dietary quality, systemic inflammation, and microbiota dysbiosis, leading to impaired nutrient utilization and metabolic dysfunction. Deficiencies in vitamin D, calcium, iron, magnesium, and B vitamins are common and often coexist with macronutrient imbalances. Diets rich in saturated fats and refined carbohydrates exacerbate inflammation and metabolic risk, whereas plant-based proteins, unsaturated fats, and fiber support metabolic resilience. Precision nutrition and biomarker-guided monitoring show promise but require validation in pediatric cohorts. Evidence on microbiota modulation and nutrient-gene interactions remains inconsistent, reflecting methodological heterogeneity. Conclusions: Malnutrition in pediatric obesity should be recognized as a distinct clinical phenotype characterized by qualitative nutrient deficiency within a state of energy surplus. Addressing this paradox demands harmonized diagnostic criteria, longitudinal biomarker surveillance, and individualized dietary strategies informed by genetics and microbiome profiling. Multilevel interventions, linking clinical practice, policy, and food system reform, are essential to prevent lifelong metabolic complications and promote healthy growth trajectories.