LITTLE ROCK, ARK. ? Forty percent of public schoolchildren in Arkansas are overweight, and nearly one in four is obese, a sign that obesity among children nationwide is probably far worse than health officials had thought.

The findings are the broadest and most recent comprehensive look at children’s weights, the result of a state law in Arkansas, where state officials have made obesity a top issue.

“I think we’ll find as we go along that Arkansas is not that much more obese than other parts of the country,” said Dr. Carden Johnston, president of the American Academy of Pediatrics. “(The) Arkansas data is the best that we have because it’s cross-sectional.”

The Arkansas numbers paint a more dire picture than previous national studies. Those have indicated that about 30 percent of American children are overweight or obese. Those falling into the obese category account for about 15 percent.

In Arkansas, about 22 percent of the children are considered obese while 18 percent are merely overweight. Fifty-eight percent are normal weight, and 2 percent underweight.

Those results, released Thursday in Williamsburg, Va., at a Time-ABC News obesity summit, represent 276,000 of Arkansas’ 450,000 public school students.

“This is a childhood issue now and it’s sobering to see the number of children who have it,” Johnston said.

Arkansas already has removed vending machines from elementary school campuses and set up a Child Health Advisory Committee to help parents get their children to normal weights.

Nationwide, two-thirds of American adults are classified as either overweight or obese by the Centers for Disease Control and Prevention.