Composition of gut microbiota and its association with body mass index and lifestyle factors in a cohort of 7–18 years old children from the American Gut Project

BACKGROUND: The association between the gut microbiota and obesity in young children and adolescents is not fully studied. OBJECTIVES: This study investigated the associations between the gut microbiota and body mass index (BMI) level (underweight, normal, overweight, obese) and lifestyles (diet type and exercise frequency), controlling for demographic and clinical factors among children aged 7-18 years. METHODS: A cohort study was conducted on 267 children aged 7-18 years from the American Gut Project. 16S rRNA sequences were analysed by QIIME 2™. Composition of gut microbiota and its associations with BMI level, weight change and lifestyles were analysed using linear decomposition model. RESULTS: Significant factors affecting the gut microbiota were BMI level (p = 0.009), exercise frequency (p = 0.003) and diet type (p = 0.01), controlling for age, sex and use of antibiotics and probiotics. More bacterial operational taxonomic units (OTUs) were associated with BMI level (120 OTUs) and diet type (122 OTUs) than exercise frequency (67 OTUs). Actinobacteria phylum had significantly depleted OTUs for BMI level, diet type and exercise frequency; Proteobacteria phylum had significantly enriched OTUs for higher BMI level and Firmicutes phylum had significantly enriched OTUs for more frequent exercise. CONCLUSIONS: Significant associations were found between the gut microbiota composition and BMI level and lifestyles controlling for demographic and clinical factors in children aged 7-18 years.