Obesity rates in U.S. adults and children have leveled off after surging for many years, the government health agency says. That's a sliver of good news, but the problem remains a nationwide epidemic.

A report released Wednesday shows more than two-thirds of adults and almost a third of children are overweight. With the new numbers, percentages have now held steady for about five years.

"Even though this finding is certainly good news, the statistics are still staggering," said Dr. J. Michael Gaziano, a contributing editor at the Journal of the American Medical Association, which published the study online.

The Centers for Disease Control and Prevention, the U.S. agency that compiled the data, reported that 34 percent of adults and 17 percent of children are obese (severely overweight).

The new data are based on health surveys involving height and weight measurements of 5,700 adults and 4,000 children, surveys the disease center does every two years.

Among children ages 2 to 19, 32 percent were at least somewhat overweight — a rate that was mostly unchanged. But disturbingly, more children were classified as extremely obese, including 15 percent of boys ages 6 to 19.

The study didn't examine the causes, but a researcher cited the usual suspects — soft drinks, video games and inactivity.