Among the more than 33,000 young children researchers followed, of those who had been breast-fed in infancy only 9% were obese, compared to 12% of those who were never breast-fed.

The findings suggest that breast-feeding has a modest protective effect against obesity, according to the report in the December issue of The Journal of Pediatrics.

While some past studies have also found that breast-feeding may reduce the risk of obesity, experts have been critical that other factors--such as maternal obesity and social class--might be responsible for the effect.

In the current study, socioeconomic status of the breast-fed and non-breast-fed children was very similar, according to Dr. Rudiger von Kries from Ludwig-Maximilians-University in Munich, Germany and colleagues.

"This suggests that the effect of breast-feeding on the prevalence of obesity is not confounded by socioeconomic status," they write.

"The strength of the effect, the consistency with observations in Western Europe/American capitalist societies, the coherence, and a number of possible biological mechanisms suggest a causal association between breast-feeding and overweight/obesity," the authors conclude.

"It is welcome news that breast-feeding may prevent excess weight gain later in childhood," Dr. Matthew W. Gillman of the Harvard Medical School (news - web sites) in Boston writes in an editorial accompanying the findings. "It makes sense to add potential obesity prevention to the list of breast-feeding's benefits."

SOURCE: The Journal of Pediatrics 2002;141:764-769,749-750.