Two Sides of a Coin: Molecular, metabolic, and Phenotypic Convergence in Pediatric Undernutrition and Obesity

This narrative review juxtaposes the metabolic and molecular consequences of pediatric under- and overnutrition, highlighting the similarities and differences between these two nutritional states occurring simultaneously in different parts of the world. Numerous biological changes in pediatric acute undernutrition and obesity have been linked to elevated risks of chronic metabolic disorders. We summarize recent evidence on pathophysiological pathways and outcomes common to both conditions. Despite etiological divergence, early-life nutritional imbalances converge on shared mechanisms and consequences with intergenerational implications. Both acute undernutrition and obesity in childhood have intersecting long-term outcomes including insulin resistance, type 2 diabetes, cardiovascular diseases, hepatic steatosis, cancers, and others, mediated through endocrine, immunological, epigenetic, and gut microbiome pathways, albeit via diverse specific mechanisms. Robust, longitudinal studies in varied geopolitical settings are needed to further elucidate the complex mechanisms, long-term phenotypic consequences, and therapeutic effects in these twin conditions.