The obesity epidemic may have peaked among U.S. children, halting a decadeslong trend of inexorably expanding waistlines among the nation's youngest and most vulnerable, federal health officials reported yesterday.

A new analysis of the most recent data collected by an ongoing government survey, considered the most authoritative on the subject, detected the first sign since the 1980s that the proportion of 2- to 19-year-olds who are overweight may have stopped rising, the National Center for Health Statistics reported.

"It looks like it's leveling off," said Cynthia Ogden, an epidemiologist whose analysis is being published in today's issue of the Journal of the American Medical Association. "It could finally be stabilizing."

More data will be needed, however, to confirm that the data represent a turnaround in the long upward trend and not just a temporary pause, Odgen noted. And even if the epidemic has peaked, the pace at which young people are becoming overweight remains alarmingly high.

Moreover, those who are already overweight face a future fraught with possible serious health problems.

"It's too soon to uncork the champagne," said David Ludwig, an expert on childhood obesity at Children's Hospital Boston who co-wrote an editorial accompanying the new research. "We're not out of the woods by any stretch. Even if the rates don't go up any more, they are so high that the full impact of the childhood obesity epidemic will continue for the next few decades."

Still, several experts said the data offer the first glimmer of hope that the country could be starting to push back against a major public health threat.

"We may be turning a corner with respect to obesity," said William Dietz, director of the Division of Nutrition, Physical Activity and Obesity at the federal Centers for Disease Control and Prevention in Atlanta. Dietz noted that the data are consistent with earlier numbers about adults nationwide and with data on children from a handful of states.

"I'm hopeful we're at a turning point," he said.

The analysis could not determine why the rate may have stalled, but experts said it could be because of a variety of factors, including rising awareness of the problem among parents, schools, community groups, and government and privately funded programs.

"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."

LITTLE CHANGE SINCE '99

The proportion of children who are obese has been rising steadily since about 1980, tripling from about 5 percent to more than 15 percent. Overweight children are prone to a host of serious health problems, including asthma, diabetes and heart disease.

Ogden and her colleagues analyzed data collected by the National Health and Nutrition Examination Survey, a nationally representative database tracking obesity and other major health issues. The study focused on the most recent data — height and weight measurements collected from about 8,165 children and adolescents as part of the 2003-04 and 2005-06 surveys. There was no statistically significant change, the researchers found.

Taken together, the weight of 31.9 percent of the youths held steady at or above the 85th percentile for their age, which is considered overweight; 16.3 percent were at or above the 95th percentile, the definition of obese; and 11.3 percent were at or above the 97th percentile for their age, which classifies them as very obese.

Moreover, when the researchers compared the two periods with surveys dating back to 1999, they found no significant increase over the entire period, strengthening their confidence that the trend had leveled off.

"After two time points it looked pretty much the same, but you need more time points to determine a trend, so it's hard to be sure. But after multiple time points that look flat, you may be cautiously optimistic that it is leveling off," Ogden said.

VARIETY OF REASONS

The trends held steady for males and females and across all racial and ethnic groups, though older children, along with blacks, Hispanics and other minorities, continued to have higher obesity rates.

"I don't want to minimize the problem," Ogden said. "It hasn't gone away. But this may be a first necessary step; it perhaps is starting to go down."

Experts offered a variety of possible explanations for the shift.

"I don't think we can pinpoint to any one thing that is responsible for the plateau, but I think it could be a gathering of a variety of strategies," Dietz said.

Barry Popkin, who heads the Interdisciplinary Obesity Center at the University of North Carolina at Chapel Hill, said he is skeptical that government programs are responsible. One possible influence, he said, is the flagging economy.

"When economic times are difficult, we always slow things down on lots of things, like eating," Popkin said.

Another possibility is that there is a limit to how many children are genetically predisposed to becoming obese, and they have already become so.

"It may be that we've reached a point where the proportion of the population genetically susceptible to obesity is already obese," said Susan Yanovski, co-director of the office of obesity research at the National Institute of Diabetes and Digestive and Kidney Diseases.

LEARN MORE

JAMA: www.jama.ama-assn.org

CDC: www.cdc.gov

The Associated Press contributed to this report.