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Breastfeeding may help to protect against overweight by modifying the gut microbiota, particularly early in life, a longitudinal Canadian study in more than 1000 infants suggests.
Mothers completed questionnaires at 3, 6, and 12 months postpartum, reporting on breastfeeding and the introduction of formula and complementary foods. Investigators collected fecal samples for microbe analysis at 3 to 4 months and at 12 months, at which time infants also were weighed and measured.
Infants fed formula were at higher risk of overweight than those who were breastfed; by 12 months, 33.3% of infants who were fed formula exclusively were overweight or at risk of overweight as were 27.6% of those who were fed both formula and breast milk. This compares with 19.2% of infants who were exclusively breastfed. Briefly being fed formula in the hospital, followed by exclusive breastfeeding, did not increase the risk of overweight.
This dose-dependent increase in risk of overweight associated with substituting formula for breast milk seemed to go in tandem with changes in microbiota that are related to overweight. (Complementary foods did not have the same effect.) Most significant, at age 3 to 4 months, was the abundance of Lachnospiraceae seen in formula-fed infants who became overweight by 12 months. Furthermore, compared with breastfeeding infants, formula-fed babies had a higher ratio of organisms associated with obesity to those known to be beneficial.
Overall, formula-fed babies had much more diverse gut bacteria, some forms of which may contribute to the risk of becoming overweight (Forbes JD, et al. JAMA Pediatr. 2018:172:e181161).
Thoughts from Dr. Burke
Formula feeding has long been linked with an increased risk of obesity. Could changes in the microbiome be the mechanism for this increased risk, and, if so, can we change the microbiome of formula-fed babies to more closely resemble that of babies fed breast milk? Watch for more to come on this topic!