IPR Research Brief

Breastfeeding in the Fight Against Obesity

Molly Metzger and Thomas McDade

A new study has confirmed the use of a highly effective tool to help curb the nation’s childhood obesity epidemic: breastfeeding.

The study, by IPR anthropologist Thomas McDade and graduate student Molly Metzger, shows that breastfed babies are on average 14 pounds lighter in adolescence when compared with their formula-fed siblings.

This within-family difference is a major step forward for obesity research, McDade explained, and holds important policy implications for programs, such as the federally funded Women, Infants, and Children (WIC), that involve obesity prevention, childhood nutrition, and lactation support for new mothers.

Although previous research had indicated that breastfeeding might be linked to adult body mass index, or BMI, an indicator of obesity, researchers had difficulty isolating breastfeeding from other family and environmental factors. It was too easily confounded with mother’s health, employment, and socioeconomic status, among others.

Using data from the nationally representative Panel Study of Income Dynamics (PSID) on more than 1,000 adolescents, McDade and Metzger got around this issue by focusing on 488 sibling pairs, who were likely to share daily routines and eating habits as well as family background.

The findings, published in the American Journal of Human Biology, show that in addition to the significant weight difference between children who were breastfed and those who were not, breastfeeding significantly reduced the likelihood of reaching obesity in adolescence for all children in the PSID sample.

“We were surprised by the magnitude of these findings,” said Metzger, the study’s lead author. “We had actually expected the causal link between breastfeeding and obesity to weaken, not strengthen, under this more rigorous research design.”

Given that a full third of U.S. teens are overweight, with 15 percent qualifying as “obese,” the researchers conclude that encouraging breastfeeding is another important tool in the fight against childhood fat—one that should be included alongside the typical emphasis on better eating and exercise habits.

“I think it is important to support mothers who wish to breastfeed and not stigmatize those who don’t or can’t,” Metzger said. “There are a number of programs and policies, from workplace supports to the WIC nutrition program, that could be improved to better support the choice to breastfeed.”

For more information about these and other IPR research projects, please visit www.northwestern.edu/ipr/.