Mothers must breastfeed for at least four months without using formula to reduce obesity risk in preschool children

Pediatric obesity researchers from Mathematica Policy Research, Inc., and Children’s Hospital of Pittsburgh have found that for breastfeeding to reduce the risk of obesity in preschool children, mothers must breastfeed for at least four months without using formula or for at least six months if they are also formula feeding.

In one of the largest studies to examine the link between breastfeeding and obesity, the researchers studied more than 73,000 low-income children. While there have been many studies examining whether breastfeeding is associated with a reduced risk of childhood obesity, it has not been clear how long mothers need to breastfeed to reduce their child’s risk of obesity. Nor has it been clear whether any protective effect of breastfeeding on childhood obesity is lessened if children are being both breastfed and formula fed. The results of the study are being published in the latest issue of Obesity Research, a journal published by the North American Association for the Study of Obesity.

Debra Bogen, MD, of Children's Hospital, Barbara Hanusa, Ph.D., of the University of Pittsburgh School of Medicine and Robert C. Whitaker, MD, a senior fellow at Mathematica, prospectively studied children enrolled in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC). Among preschool children who were breastfed for at least four months without formula or at least six months with formula, the risk of obesity was reduced by 30 to 45 percent. However, this beneficial effect of breastfeeding was found only among white children whose mothers did not smoke during pregnancy. Furthermore, less than 10 percent of children were breastfed long enough to receive the benefit. Nearly 12 percent of the children in the study were considered obese, as measured by having a body mass index (BMI) at or above the 95th percentile.

"While breastfeeding may prevent childhood obesity, we have found that children must be breastfed without added formula for at least four months in order to reduce the risk of obesity. Currently in the United States, few women are breastfeeding long enough to have an impact on childhood obesity," Dr. Bogen said. "We need to change social and health policies in order to support breastfeeding for a longer period of time if we are going to have an impact on the incidence of obesity through breastfeeding."

“While no one knows the reason why breastfeeding may protect against later obesity, it is possible that breastfeeding, compared to bottle feeding, allows infants to have more control in when they eat and how much they eat,” said Whitaker, a senior fellow at Mathematica and a study co-investigator. “Allowing infants to regulate their own food intake early in brain development may be important for establishing long-term patterns of healthy appetite regulation.” This hypothesis is consistent with the study findings that the protective effect of breastfeeding on later obesity only occurs when breastfeeding is sustained and is stronger when breastfeeding occurs without bottle feeding of formula.

Mathematica, a nonpartisan firm, conducts policy research and surveys for federal and state governments, as well as private clients. The employee-owned company, with offices in Princeton, N. J., Washington, D.C., and Cambridge, Mass., has conducted some of the most important studies of nutrition, welfare, health care, education, employment, and early childhood policies and programs in the United States. Mathematica strives to improve public well-being by bringing the highest standards of quality, objectivity, and excellence to bear on the provision of information collection and analysis to its clients.