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.

Background: In pediatric celiac disease (CD), intestinal malabsorption and the restrictive nature of a gluten-free diet (GFD) frequently result in persistent macro- and micronutrient imbalances, despite histological remission. The present review evaluates the evidence on nutritional adequacy of the GFD, identifies common deficiencies, and considers biomarker strategies and dietary recommendations to optimize growth and metabolic health. Methods: A narrative review of the literature was conducted, focusing on studies of nutrient intake, product composition of gluten-free foods, biomarker assessment, and clinical outcomes in children with CD. Both macronutrient (protein, fat, carbohydrate, fiber) and micronutrient (iron, vitamin D, calcium, B-vitamins, zinc, magnesium) domains were included. Results: Children with CD on long-term GFD demonstrate higher intake of lipids (especially saturated fat) and simple carbohydrates, alongside consistently low intake of dietary fiber and key micronutrients. Gluten-free products often exhibit lower protein content, higher glycemic index, and reduced fortification compared to gluten-containing equivalents. Nutritional deficits contribute to impaired linear growth, delayed puberty and increased metabolic risk. Conclusions: Nutritional adequacy of the GFD cannot be assumed in children with CD. Routine monitoring using standardized biomarker panels, combined with personalized dietary counseling and improved formulation and fortification of gluten-free products, is essential to mitigate long-term adverse outcomes. Future work should advance precision nutrition approaches and public-health initiatives to optimize dietary quality in this vulnerable population.

Background: In pediatric celiac disease (CD), intestinal malabsorption and the restrictive nature of a gluten-free diet (GFD) frequently result in persistent macro- and micronutrient imbalances, despite histological remission. The present review evaluates the evidence on nutritional adequacy of the GFD, identifies common deficiencies, and considers biomarker strategies and dietary recommendations to optimize growth and metabolic health. Methods: A narrative review of the literature was conducted, focusing on studies of nutrient intake, product composition of gluten-free foods, biomarker assessment, and clinical outcomes in children with CD. Both macronutrient (protein, fat, carbohydrate, fiber) and micronutrient (iron, vitamin D, calcium, B-vitamins, zinc, magnesium) domains were included. Results: Children with CD on long-term GFD demonstrate higher intake of lipids (especially saturated fat) and simple carbohydrates, alongside consistently low intake of dietary fiber and key micronutrients. Gluten-free products often exhibit lower protein content, higher glycemic index, and reduced fortification compared to gluten-containing equivalents. Biomarkers including prealbumin, ferritin, 25-hydroxyvitamin D, and inflammatory mediators aid in early detection of malnutrition. Nutritional deficits contribute to impaired linear growth, delayed puberty and increased metabolic risk. Conclusions: Nutritional adequacy of the GFD cannot be assumed in children with CD. Routine monitoring using standardized biomarker panels, combined with personalized dietary counselling and improved formulation and fortification of gluten-free products, is essential to mitigate long-term adverse outcomes. Future work should advance precision nutrition approaches and public-health initiatives to optimize dietary quality in this vulnerable population.

Background/Objectives: Fabry Disease (FD) is a multisystem X-linked lysosomal storage disorder that often manifests with nonspecific gastrointestinal (GI) symptoms, such as abdominal pain, diarrhea, and constipation. These symptoms may appear early in childhood, severely impacting quality of life and delaying diagnosis, and may be linked to nutritional challenges. This systematic review aims to evaluate the prevalence, characteristics, clinical relevance, and nutritional aspects of GI manifestations in pediatric FD patients to aid in early recognition and improve outcomes. Methods: A systematic literature search with meta-analysis adhering to PRISMA and MOOSE guidelines was conducted across PubMed, Web of Science, and Google Scholar from inception to November 2024 using fixed inclusion and exclusion criteria. Data were extracted by two reviewers independently. Disagreements were resolved by consensus; a third reviewer was consulted, when necessary. Pooled analysis was performed by a random-effects model; heterogeneity was assessed using the I² method. A quality assessment appraisal of the studies was carried out using the ROBINS-I tool. Results: The review encompassed 18 studies involving 736 pediatric patients. The evaluation of the pooled prevalence of GI symptoms in FD patients was 53% (95% CI 38–68%, I² 90%), with abdominal pain being the most frequent (pooled prevalence of 46% (95% CI 33–60%, I² 86%)). Symptoms often presented early, with a summarized standardized mean difference between the mean age of symptom onset and the mean age at FD diagnosis of 2.07 years (95% CI of 0.56–3.57, I² 42%, p < 0.01). Nutritional issues, including reduced food intake and potential malabsorption, were reported in cases with severe GI symptoms, contributing to growth impairments. Conclusions: GI symptoms frequently constitute the earliest clinical manifestation of FD in children. Their nonspecific nature underscores the importance of heightened clinical suspicion for timely diagnosis. Early intervention, including enzyme replacement therapy and tailored nutritional strategies, can alleviate symptoms, improve quality of life, and prevent disease progression. Multidisciplinary approaches are essential to optimize patient outcomes and further research into the pathophysiology and management of GI symptoms in FD is warranted.