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There's another sign that childhood obesity may be on the decline nationwide.

    A government study finds that obesity among children ages two to five has dropped to 8 percent -- from 14 percent a decade ago. But the decline was only seen in pre-schoolers, not in older children.

    And some experts point out that even the improvement in toddlers wasn't a steady decline. They say it's hard to know whether the weight figures for pre-schoolers are permanently curving down.

    The report appears online in the Journal of the American Medical Association.

    Health officials have been hoping for more substantial evidence that they've turned a corner in the fight against childhood obesity.

    A third of U.S. children and teens, and more than two-thirds of adults, are obese or overweight. It's seen as one of the nation's leading public health problems. Health officials call it a longstanding epidemic.

    Pre-schoolers who are overweight or obese are five times more likely than other children to be heavy as adults. That means a greater risk of high cholesterol, high blood sugar, asthma and even mental health problems.