"That is a first encouraging finding in what has been unremittingly bad news," said Dr. David Ludwig, director of an obesity clinic at Children's Hospital Boston. "But it's too soon to know if this really means we're beginning to make meaningful inroads into this epidemic. It may simply be a statistical fluke."
Overall, roughly 32 percent of children were overweight but not obese, 16 percent were obese and 11 percent were extremely obese, in a study based on in-person measurements of height and weight in 2005 and 2006.
Those levels were roughly the same as in 2003-04 after a steady rise since 1980, according to the federal Centers of Disease Control and Prevention, which conducted the study.
"Maybe there is some reason for a little bit of optimism," said CDC researcher Cynthia Ogden, the study's lead author.
Some experts said that if the leveling-off is real, it could be because more schools and parents are emphasizing better eating habits and more exercise. Even so, they and Ogden stressed that it would be premature to celebrate.
"Without a substantial decline in prevalence, the full impact of the childhood epidemic will continue to mount in coming years," Ludwig said. That is because it can take many years for obesity-related complications to translate into life-threatening events, including heart attacks and kidney failure.
He co-wrote an editorial accompanying the study in Wednesday's Journal of the American Medical Association. He had no role in the research.
The results are based on 8,165 children ages 2 to 19 who participated in nationally representative government health surveys in 2003-04 and 2005-06.
The surveys are considered the most accurate reflection of obesity levels because they are based on in-person measurements rather than relying on people's own reports.
CDC data reported last year showed obesity rates for men also held steady from 2003-04 to 2005-06 at about 33 percent after two decades of increases. The rate for women, 35 percent, remained at a plateau reached in 2003-04.
The CDC's analysis of data for 2007-08, due next year, may be the best evidence for determining what direction children's rates are really heading, Ludwig said.
Dr. Reginald Washington, a children's heart specialist in Denver and member of an American Academy of Pediatrics obesity committee, said "the country should be congratulated" if the rates have in fact peaked.
One way to get kids to take off the pounds is by getting them on their feet. Kay Morris launched "Marathon Kids" in Austin and, reports CBS News correspondent Sandra Hughes.
"We're not trying to build marathon runners," Morris said. "We're just trying to move children from sedentary to non-sedentary."
In Los Angeles, Allesandro Elementary joined the running program, reports Hughes. The kids are healthier and there's a bonus: Academic performance is up significantly - 23 points on standardized tests.
"There are a lot of people trying to do good things to try to stem the tide," Dr. Washington said. Some schools are providing better meals and increasing physical education, and Americans in general "are more aware of the importance of fruits and vegetables," he said.
On the other hand, he noted that he recently treated an obese young patient "who in three days did not have a single piece of fresh fruit.
"We still have a long ways to go," he said.