Associations Between Rapid Infant Weight Gain, Infant Feeding Practice and the Infant Gut Microbiome

Background: Rapid infant weight gain (RWG) by six months of age has been identified as one of the earliest indicators of childhood obesity. Previous research suggests that exclusive breastfeeding over formula feeding may serve a protective effect from RWG. In addition, the makeup of the infant gut microbiome may influence RWG as differences in feeding practices have been shown to alter the bacterial makeup of the gut, potentially impacting energy metabolism. However, little research has been conducted investigating the potential relationships between RWG, infant feeding practices, and the infant gut microbiome.Methods: This study was a pilot study, which included 31 mother-infant dyads who were primarily recruited from Women, Infant, and Children’s Supplemental Nutrition Program (WIC) clinics and by word of mouth in the Southwestern United States. Participants were followed over six months, with study staff conducting home study visits four times (pregnancy, two days postpartum, three weeks and six months). Mothers who participated in this study were majority White (n=40.6%), non-Hispanic or Latino (67.7%), and obtained a graduate degree (n=22.6%). Participants were included in this analysis (n=22) if they provided at least two infant fecal samples, and the study staff were able to collect infant anthropometric data at the three-week and six-month study visits. Microbial DNA from fecal samples was sequenced using the Illumina MiSeq instrument after polymerase chain reaction (PCR) amplification was performed on the V4 region of the 16S rRNA gene sequence. Statistical analysis was performed using the QIIME2 longitudinal plug-in. Results: Results of this study suggested a significant difference in weighted UniFrac between infants who were exclusively breastfed and formula-fed from birth to three weeks of age. Additionally, an exploratory statistical method identified family Prevotellaceae as a potentially volatile microbe; however, this model failed to reach significance for either RWG or mode of feeding. Overall, no additional alpha or beta diversity metrics or differential abundance of microbes by either RWG or feeding practice group was found in this study. Conclusion: Future research is warranted to further explore potential connections between RWG, infant feeding practices, and the infant gut microbiome in a longitudinal study with a larger sample size.