Association Between Overweight and Obesity and the Occurrence of Small Intestinal Bacterial Overgrowth (SIBO) in Children and Adolescents Referred for Gastrointestinal Symptoms: A Cross-Sectional Study with Analysis of Patients’ Demographic Character

Background/Objectives: Small intestinal bacterial overgrowth (SIBO) is considered an important cause of gastrointestinal symptoms and nutrient malabsorption in children. SIBO has traditionally been associated with undernutrition and malabsorption syndromes. Yet, growing evidence suggests its possible relationship with overweight, obesity, and metabolic disturbances. The influence of demographic factors, nutritional status, and gastrointestinal symptoms on the occurrence of SIBO in pediatric populations is still unclear. Therefore, the aim of this study was to assess the prevalence of SIBO in children and adolescents referred for gastrointestinal symptoms, and its association with demographic characteristics, nutritional status, carbohydrate malabsorption, and gastrointestinal symptoms. Methods: A cross-sectional study was conducted on 495 children and adolescents referred for hydrogen breath testing due to gastrointestinal symptoms. Demographic characteristics, nutritional status, gastrointestinal symptoms, SIBO test results, and carbohydrate malabsorption test outcomes were analyzed. Nutritional status was assessed using age-specific growth criteria, with World Health Organization (WHO) standards applied in children younger than 3 years and body mass index (BMI) percentile categories based on Polish reference standards used in participants aged 3–18 years. Associations between SIBO and demographic, clinical, and nutritional variables were evaluated using appropriate statistical tests and univariate analysis. Results: Of 495 participants, SIBO was diagnosed in 60.2% of them. No significant associations were found between SIBO and sex, age, place of residence, or nutritional status categories (p > 0.05). However, a strong association was observed between positive SIBO test results and positive carbohydrate malabsorption test results (p < 0.001). Belching was the only symptom significantly associated with a positive SIBO result (OR = 2.05; 95% CI: 1.10–3.80; p = 0.023). Conclusions: Although no significant association was found between SIBO and nutritional status categories, positive SIBO test results tended to occur more frequently in children with both undernutrition and excess body weight, and were strongly associated with carbohydrate malabsorption.