The percentage of American children who are overweight or obese appears to have levelled off after a 25-year increase, according to new figures that offer a glimmer of hope in an otherwise dismal battle.

"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 per cent of children were overweight but not obese, 16 per cent were obese and 11 per cent 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 U.S. 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 levelling-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.

Obesity rates remain steady for men and women

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 per cent, after two decades of increases. The rate for women, 35 per cent, 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.

"There are a lot of people trying to do good things to try to stem the tide," 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.