The good news is that after decades of furious growth, obesity rates finally seem to be leveling off in the U.S. The bad news is that America's youth still appear to be dangerously unaware of the problem.

Forty-two percent of obese children and adolescents in the U.S.—ages 8 to 15—misperceive their weight as normal, according to a new report (pdf) by the Centers for Disease Control and Prevention's National Center for Health Statistics. Among obese boys, the rate is almost 48 percent; for obese girls, it's roughly 36 percent. And America's overweight children are even more confused about the relative size of their respective waistlines—some three quarters of overweight children and teens consider themselves to be "about the right weight."

The prevalence of weight misperception isn't only characteristic of the country's heavier children. About one half of America's underweight children don't know they're underweight, and roughly a third of all kids in the U.S.—overweight, underweight, and just-the-right weight—mistake their weight status for something other than it is.

But given the exceptionally high rate of obesity among American adults—which is the highest of any major country (paywall) in the world—the lack of self-perception found in the country's obese children should be particularly alarming. Nearly a third of kids in the U.S. are considered overweight, according to the Food and Research Action Center, and roughly 35 percent of them now go on to become obese in adulthood.

Obesity is both a national health epidemic—while it is considered a disease itself, it has also been linked to a number of other conditions, including heart disease, stroke, and type 2 diabetes—and a serious economic problem—as of 2008, the annual medical costs alone of obesity amounted to almost $150 billion, according to the CDC.

It's also at the center of the country's public school lunch program overhaul, which has been a key policy issue for first lady Michelle Obama. Ongoing debates, which range from what should be considered a vegetable serving to whether new, healthier options are making kids skip out on lunch entirely, have become especially heated with the new school year approaching. And there's good reason to believe recent menu tweaks haven't gone far enough—a number of junk food items, including Cheetos, funnel cake, and Domino's, were among those flaunted at the School Nutrition Association's latest annual conference.

The fact that so many overweight American children and teens don't know they're overweight is worrisome, because it's likely to perpetuate the country's overeating (and under-exercising) problem. "Accurate self-perception of weight status has been linked to appropriate weight control behaviors in youth," the CDC report says. A study conducted in 2011 found that weight perception was more likely to effect changes in exercise and eating habits than actual weight status. "Children who don't have a correct perception of their weight don't take steps to lose weight," Neda Sarafrazi, one of the report's authors, told NPR.

It's unreasonable to expect America's youth to take better care of themselves if they aren't even aware that they have to.