Breastfeeding is no magic bullet against obesity, according to research that contradicts previously held beliefs about the scope of human milk’s capability.
“There’s a lot of other evidence out there to continue to support breast-feeding,” says the study’s lead author Dr. Richard Martin, a professor of clinical epidemiology at the University of Bristol in the U.K. “But in terms of breastfeeding reducing obesity, it’s unlikely to be effective.”
Martin worked with colleagues at Harvard University and McGill University in Montreal to assess 15,000 mothers in Belarus. The location was intentional — when the study began in 1996, breastfeeding was not a popular practice among Belarusian mothers. By separating the moms-to-be into two groups — one that gave birth at hospitals where staff received “Baby-Friendly” training designed to encourage breastfeeding, while the other delivered at hospitals that provided no extra support for the practice — researchers were able to create a “huge contrast” in a setting where breastfeeding rates were historically low. After three months, 43% of babies in the first group were exclusively breastfeeding compared to just 6% in the group that were born in hospitals that had no extra training.
The babies were followed up in 1997 — their first year of life — and again when they reached 6 ½ and 11 ½. The breastfed babies experienced fewer gastrointestinal infections, less eczema and higher IQ (they scored about 7 ½ points higher than their formula-fed friends at age 6 ½). There was no difference in dental cavities, allergies, asthma or rates of being overweight or obese.
The latest report, published in the Journal of the American Medical Association (JAMA) marks the first release of data from the 11 ½-year old participants. Mirroring the earlier results, the researchers found no changes in weight and body fat between those who were breast-fed and those who weren’t. About 15% of the children in both groups were overweight, and 5% were considered obese.
Comparing body mass index (BMI) or measures such as waist circumference and skin thickness yielded “absolutely nothing that was statistically significant,” says Martin.
These results contradict previous studies that found breast-feeding cuts the rates of overweight or obesity among children. Experts believed the practice helped to lower obesity rates because it encourages babies to eat until they’re full as opposed to forcibly finishing bottles, even if they feel full. But these studies may have been documenting the effect of other, confounding factors on children’s weight. Mothers feed babies based on how much weight the infants gain, as well as the toddlers’ eating habits, so it’s possible that some of the breastfed babies happened to be heavier to begin with, and that in turn prompted their mothers to feed them less.
In the current study, however, Martin hoped to avoid some of that potential bias by studying babies who were randomly assigned to be breastfed or bottle-fed. That allowed the researchers to control for other factors that could influence results — dietary choices, for example, or education levels.
“If you look at the characteristics of women who choose to breast-feed, they are very different from women who don’t,” says Martin. In the U.K., for example, 90% of women who attend college initiate breast-feeding compared to just 30% of women who don’t enroll.
The results strongly suggest that breastfeeding may not be the answer to the obesity epidemic, but Martin says the outcomes shouldn’t alter existing recommendations. For proper health and nutrition, the World Health Organization advises that babies be exclusively breastfed for the first six months, and for up to two years if needed. The American Academy of Pediatrics suggests that moms breast-feed exclusively for about six months and continue breast-feeding to some extent for at least a year. But while 75% of U.S. mothers start out nursing their babies, only 44% are still doing so by the time their child is 6 months old.
If anything, the success of the Baby-Friendly initiative in the Belarusian hospitals should offer inspiration to U.S. birthing centers hoping to boost their own breast-feeding rates. Baby-Friendly hospitals encourage several practices that could make feeding easier, some of which I detailed in an article about ways to improve breastfeeding rates, including breast-feeding when the baby requires as opposed to on a schedule, offering newborns only breast milk, as well as actively helping new mothers learn how to breast-feed:
Hospitals play a critical role in jump-starting a successful breast-feeding relationship, and those that are most committed to getting breast-feeding off to a good start — by encouraging babies to remain in their mothers’ hospital rooms where they can nurse on demand, for example, or breaking the tradition of sending new moms home with free formula samples in diaper bags paid for by formula manufacturers — are getting certified as “Baby-Friendly” facilities. But only 4% of hospitals can claim that distinction.
“I think it starts with hospitals, which need to support mothers to feel confident when they leave,” says lead author Cria Perrine, an epidemiologist at the Centers for Disease Control and Prevention (CDC) who focuses on infant feeding. “Employers and families have to be on board, and communities have to be comfortable with women breast-feeding in public. But hospitals are the front line. If women don’t even get started, there’s no way they can meet their goals.”