The Effects of Breastfeeding on Childhood BMI: A Propensity Score Matching Approach

L A Gibson, M Hernandez Alava, M P Kelly, M J Campbell


This paper investigates the effect of breastfeeding on childhood body mass index (BMI). We use data from the Millennium Cohort Study (MCS), a nationally representative UK cohort survey, containing detailed infant feeding information, which allow us to explore the effects of a range of breastfeeding variables on the mean BMI of children breastfed for different durations and for exclusive and partial breastfeeding.

Using propensity score matching, we find statistically significant influences of breastfeeding on childhood BMI, particularly in older children and when breastfeeding is prolonged and exclusive. The effects of breastfeeding on BMI are small in magnitude but large relative to the mean BMIs of children this age. At this young age, there is not a large difference in BMI between children who are identified as obese and those who are identified as normal weight, so even a small difference in BMI could mean the difference between children being overweight or a healthy weight. We suggest that breastfeeding should be encouraged as part of wider lifestyle interventions in order to help reduce BMI as well as improve other childhood outcomes. This could be important evidence for public health bodies when creating public health guidelines and recommendations.