lose weight

Kids could be cruel, especially about weight. So you may think obese or overweight children know very well that they are heavy -- because of playground politics. But that's not necessarily so, based on government data covering about 6,100 kids and teenagers ages 8-15.

About 30 % "misperceived" their weight status (underweight, normal weight, obese or overweight), according to a study from the Centers for Disease Control and Prevention's National Center for Health Statistics. (The CDC bases those categories on bmi, adjusted for gender and age.)

Among children and teenagers who were actually designated by the CDC as overweight -- or between the 85th and 95th percentiles on the CDC's growth chart -- 76 percent thought they were "about right;" about 23 percent said they were overweight. Among obese kids and teenagers (those who work in the 95th percentile and better around the CDC's charts), roughly 42 percent thought these were OK weightwise, while 57 percent thought these were within the "overweight" category. Boys, younger kids and kids from poorer families were more prone to misperceive their status.

Same with it bad if a kid doesn't know he's overweight? The report notes that research has linked knowing your weight status to trying to change behaviors.

"Children who don't have a correct thought of their weight do not take steps to lose weight," for example increasing exercise or changing eating routine, Neda Sarafrazi, a nutritional epidemiologist with NCHS and an author of the report, tells Shots.

Other research has suggested that oldsters are in the dark regarding their kids, too, about half underestimating their overweight or obese child's weight. Sarafrazi says it's key for parents to understand the reality.

But kids and teenagers already worry a lot about their weight, as an NPR parenting panel discussed recently.

Marlene Schwartz, a psychologist and director from the Rudd Center for Food Policy & Obesity at Yale University, tells Shots that while she's a large proponent of keeping tabs on kids' BMIs in the aggregate, she's not sure it's helpful to label kids as overweight. More helpful, she says, is giving kids feedback regarding their health and fitness and just what they eat -- noting ways to improve.

And when youngsters are obese, or are experiencing weight-related medical problems, Schwartz says, it's easier to encourage them to get healthier by eliminating snacking in front of the television, or cutting out sugary drinks, than to let them know they need to lose 20 pounds to be considered "just right."

"Shame is a terrible motivator," she says.

The disconnect occurred mostly -- but not exclusively -- among kids who were heavier than average. From the children who were normal weight, most knew it, while under 4 % thought they were overweight and less than 9 % thought they were too thin. Contributing to 49 percent of underweight kids thought they were about right; the rest knew these were too thin.