Childhood body mass index and associations with infant gut metabolites and secretory IgA: findings from a prospective cohort study

Background/Objectives Differences in gut microbiota, metabolites and immune markers have been observed between individuals with and without obesity. Our study determined the temporal association between infant fecal gut metabolites, sIgA and body mass index (BMI) z score of preschool children, independent of pre/postnatal factors. Subjects/Methods The study includes a subset of 647 infants from the CHILD Cohort Study (recruited between January 1, 2009, and December 31, 2012). Fecal metabolites and sIgA were measured at 3–4 months of age, and age and sex adjusted BMI z scores at 1 and 3 years of age. Associations between the metabolites, IgA, and child BMI z scores at age 1 and 3 years were tested using linear regression adjusted for pre/postnatal factors (breastfeeding, birthweight-for-gestational age, birthmode and IAP, solid food introduction). Results Mean BMI z score for all infants was 0.34 (SD 1.16) at 1 year ( N = 647) and 0.71 (SD 1.06) at 3 years ( N = 573). High fecal formate in infancy was associated with a significantly lower BMI z score (adjusted mean difference −0.23 (95% CI −0.42, −0.04)) and high butyrate was associated with a higher BMI z score (adjusted mean difference 0.21 (95% CI 0.01, 0.41)) at age 3 years only. The influence of formate and butyrate on BMI z score at age 3 were seen only in those that were not exclusively breastfed at stool sample collection (adjusted mean difference for high formate/EBF- group: −0.33 (95%CI −0.55, −0.10) and 0.25 (95% CI 0.02, 0.47) for high butyrate/EBF- group). No associations were seen between sIgA and BMI z score at age 1 or 3 years in adjusted regression models. Conclusion and relevance Differences in fecal metabolite levels in early infancy were associated with childhood BMI. This study identifies an important area of future research in understanding the pathogenesis of obesity.