No association between the early-life gut microbiota and childhood body mass index and body composition

Background: The gut microbiota has been implicated in adult obesity, but the causality is still unclear. It has been hypothesized that an obesity-prone gut microbiota can be established in infancy, but only few studies have examined the early-life gut microbiota in relation to obesity in childhood, and no consistent associations have been reported. Here, we examine the association between the early-life gut microbiota and body mass index (BMI) development and body composition throughout childhood. Methods: Gut microbiota from stool were collected from 700 children in the Copenhagen Prospective Studies on Asthma in Childhood₂₀₁₀ (COPSAC₂₀₁₀) cohort at ages of 1 week, 1month, 1 year, 4 years, and 6 years and analyzed by 16S rRNA gene sequencing. Outcomes included BMI World Health Organization (WHO) Z scores (zBMI), overweight (zBMI > 1.04) and obesity (zBMI > 1.64) (0–10 years), and adiposity rebound and body composition from dual-energy X-ray absorptiometry at 6 years. Findings: The early-life gut microbiota diversity, overall composition, and individual taxon abundances in unsupervised and supervised models were not consistently associated with either current or later BMI Z scores, overweight, obesity, adiposity rebound, or body composition in childhood. Conclusions: In a deeply characterized longitudinal birth cohort, we did not observe any consistent associations between the early-life gut microbiota and BMI or risk of obesity in later childhood. While this does not conclusively rule out a relationship, it suggests that if such associations exist, they may be more complex and potentially influenced by factors emerging later in life, including lifestyle changes. Funding: COPSAC is funded by private and public research funds (all listed on www.copsac.com).