Researchers at the University of Glasgow in Scotland have found that infants who are breast-fed could have a 30 percent reduced risk of childhood obesity compared with infants given formula.
"This is another piece of evidence that 'breast is best,'" says John Reilly, principal investigator of the study, the largest of its kind, which appears in the June 8 issue of The Lancet.
"It's very much in line with a number of papers that have been published recently, which basically show the same thing -- a modest but significant reduction in obesity," says Dr. Lawrence Gartner, who heads the American Academy of Pediatrics' executive committee on breast-feeding. "It looks like a good piece of work, and it is certainly a large population."
Reilly calculated the body-mass index (BMI) of 32,200 Scottish children when they were 39 to 42 months old, then correlated these figures with whether or not the kids had been exclusively breast-fed for their first 6 to 8 weeks.
Those who were exclusively breast-fed had a modestly lower risk of being obese, with obesity defined as being in the top two percent for BMI. The risk remained low for breast-fed children even after adjusting for socioeconomic status, birth weight and gender.
Although the results of this study are applicable only for children to age 3, other evidence suggests that the protective effect should persist and perhaps even grow stronger over time, say the study authors.
There are also significant public-policy implications.
"For obesity prevention, we have few, if any, strategies which have been demonstrated to work, so being able to establish formula-feeding as a risk factor is important," says Reilly, who is a senior lecturer in the University of Glasgow's Department of Human Nutrition.
"Breast-feeding is not a panacea for obesity, but it is now established as a beneficial strategy, can be adopted by a large segment of the population, is safe, and has lots of other health and social benefits to mother and child," he adds.
What is not exactly clear is why breast-fed children are less likely to be fat.
According to Carol Huotari, manager of La Leche League's Center for Breast-Feeding Information, babies nursing at the breast stop when they're full, whereas formula-fed infants are subject to the "clean-slate syndrome," in which their parents try to control how much they're fed.
There are also a number of possible metabolic causes, Reilly adds. For instance, she says, formula has higher plasma insulin than breast milk and could promote fat deposits.
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