Atlanta (AP) -- A new study challenges the widely held belief that breast feeding prevents a child from becoming fat as an adult.

The conclusion is based on the largest study to date on breast-feeding and its effect on adult obesity.

Lead author Karin Michels, of Harvard Medical School, says breast feeding has lots of benefits, but it doesn't prevent excess weight in children. Some health officials say 15 to 20 percent of obesity could be prevented through breast-feeding.

A spokesman for the Centers for Disease Control and Prevention says many studies have linked breast-feeding and lower rates of childhood obesity. He would not comment on the latest research.

The Harvard study is published online this week in the International Journal of Obesity.

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