Forbes JD, et al. - The association between breastfeeding, microbiota, and risk of overweight during infancy, accounting for the type and timing of supplementary feeding, was investigated. Outcomes suggest that protection against overweight is conferred by breastfeeding via modifying the gut microbiota, particularly during early infancy. Changes in microbiota are stimulated by formula feeding which are associated with overweight, whereas other complementary foods do not stimulate such changes.

Methods

• Researchers undertook this study of a subset of 1087 infants from the prospective CHILD pregnancy cohort recruiting mothers from January 1, 2009, to December 31, 2012.
• From February 1 to December 20, 2017, they performed statistical analysis.
• Feeding reported by mothers and documented in hospital records was assessed as the main outcome measure.
• They characterized fecal microbiota at 3 to 4 months (from 996 infants) and/or 12 months (from 821 infants) by 16S ribosomal RNA sequencing.
• They considered infants with a weight for length exceeding the 85th percentile to be at risk for overweight.

Results

• Researchers included 1087 infants in the study (507 girls and 580 boys).
• Maternal report at 3 months suggested 579 of 1077 (53.8%) were exclusively breastfed.
• Covariate-adjusted models showed an increased risk of overweight in infants who were exclusively formula fed at 3 months (53 of 159 [33.3%] vs 74 of 386 [19.2%]; adjusted odds ratio, 2.04; 95% CI, 1.25-3.32).
• Attenuation of this association was noted (adjusted odds ratio, 1.33; 95% CI, 0.79-2.24) after further adjustment for microbiota features characteristic of formula feeding at 3 to 4 months, including higher overall richness and enrichment of Lachnospiraceae. 
• Of 579 infants who were exclusively breastfed, 179 (30.9%) received formula as neonates; this brief supplementation was correlated with lower relative abundance of Bifidobacteriaceae and higher relative abundance of Enterobacteriaceae at 3 to 4 months, however, it did not influence the risk of overweight.
• According to feeding practices at 6 months, microbiota profiles showed significant differences at 12 months.
• Among partially breastfed infants, formula supplementation was associated with a profile similar to that of nonbreastfed infants (higher diversity and enrichment of Bacteroidaceae), whereas the introduction of complementary foods without formula was associated with a profile more similar to that of exclusively breastfed infants (lower diversity and enrichment of Bifidobacteriaceae and Veillonellaceae).
• Risk of overweight was noted to have strong association with microbiota profiles at 3 months than with microbiota profiles at 12 months.