London School of Hygiene & Tropical Medicine

Infants who are breastfed could have a reduced risk of being overweight in the first year of life, and that the protective association is stronger with longer and more exclusive breastfeeding, according to a new study published in Pediatrics.

Conducted by the London School of Hygiene & Tropical Medicine and the University of Manitoba, Canada, the study looked at both body mass index (BMI) and the rate of infant weight gain—an important predictor of future obesity and cardiovascular health. It found that the risk of overweight at 12 months of age was over three times higher among infants who were not breastfed (8.3% overweight) compared with infants who were exclusively breastfed (2.4% overweight) for the first six months of life.

Importantly the protective effects of breastfeeding were ‘dose dependent,’ meaning that babies who were partially breastfed also received some benefit, so ‘every feed counts’.

The research team used data from more than 2,500 infants and their mothers participating in the CHILD Study—a Canadian birth cohort study that is tracking children from before birth to school age and beyond to identify the root causes of asthma, allergy, obesity and other chronic conditions. Newborn feeding was documented from hospital records, and families enrolled in the study provided information about their babies’ breastfeeding status and diet at birth, and at three, six, 12, 18 and 24 months of age.

Dr Meghan Azad from the University of Manitoba who led the study and conducted the research at LSHTM, said: “Our study also found that the method of feeding breastmilk matters. Feeding expressed breastmilk from a bottle appeared to have a weaker beneficial effect on infant weight compared with direct feeding at the breast, although expressed milk was still beneficial compared to infant formula.”

Dr Azad suggests that possible explanations for the differences between direct and indirect breastfeeding include: the routine steps between pumping and feeding breastmilk (freezing, thawing and heating) may degrade the bioactive components of breastmilk; or infants who are fed at the breast may have better self-regulation of milk intake.

The study also uniquely distinguished between partial breastfeeding mixed with formula versus partial breastfeeding mixed with foods.

Dr. Azad said: “Breastfed infants supplemented with formula were at increased risk for becoming overweight at one year of age compared to breastfed infants supplemented with solid foods between five to six months. Ultimately, our hope is that this research will help to inform and optimize infant feeding guidelines, and promote programs and policies to support direct breastfeeding, such as paid maternity leave. Together, these measures could have a meaningful impact on preventing childhood obesity.”

The authors acknowledge limitations of the study, including that they did not capture information on feeding styles, nor the relative amount of pumped milk vs. direct breastfeeding.

Publication

Meghan B. Azad, Lorena Vehling, Deborah Chan, Annika Klopp, Nathan C. Nickel, Jonathan M. McGavock, Allan B. Becker, Piushkumar J. Mandhane, Stuart E. Turvey, Theo J. Moraes, Mark S. Taylor, Diana L. Lefebvre, Malcolm R. Sears, Padmaja Subbarao. Infant Feeding and Weight Gain: Separating Breast Milk From Breastfeeding and Formula From Food. Pediatrics. DOI:10.1542/peds.2018-1092