Between 1988 and 2010, the number of parents who could correctly identify their children as overweight or obese went down, according to a new study.

"Today, almost one out of every three kids is overweight or obese," said senior author Dr. Jian Zhang of the Jiann-Ping Hsu College of Public Health at Georgia Southern University in Statesboro. "They are at significantly increased risk of a number of diseases as they grow older, including diabetes, cardiovascular disease, osteoarthritis and cancer."

The first step to dealing with any problem is, of course, being aware of it, he said.

Zhang and his team examined height and weight data on 2,871 children, ages six to 11, from the 1988 to 1994 National Health and Nutrition Examination Survey and 3,202 similar kids from the 2005 to 2010 cycles of the survey.

In all cases, the children's parents were asked if they considered their child 'overweight, underweight, just about the right weight, or don't know.'

In the 1988 to 1994 data set, 78 percent of parents of an overweight boy and 61 percent of parents of an overweight girl, identified the child as 'about the right weight.' That number increased to 83 percent for boys and 78 percent for girls in the 2005 to 2010 period.

Similarly, for obese boys, 26 percent of parents said they were 'about the right weight' in 1988 compared to 37 percent in 2010, according to results in Pediatrics.

Like their parents, many kids also identify themselves as about the right weight even if they are overweight or obese, and those kids are less likely to try to lose weight (see Reuters story of August 6, 2014 here: reut.rs/1oGOJxf).

The increasing trend of weight underestimation is alarming, Zhang told Reuters Health by email.

"Studies overwhelmingly show that parental perceptions of their child's weight influence family readiness to foster healthy behaviors and increasingly underestimating puts more kids at the risk of becoming overweight or obese," he said.

Other studies have shown that overweight adults are increasingly not perceiving themselves as overweight, said Mary A. Burke, a senior economist in the research department of the Federal Reserve Bank of Boston.

Burke was not part of the new study.

The misclassification rate was quite high for both time periods, she told Reuters Health by phone.

"For six to 11 year old children, a lot of parents could say 'I'm waiting to make a pronouncement because kids are always changing, they may grow out of it'," she said.

And 'about the right weight' could reasonably include some kids who are slightly overweight but close to the healthy weight category, she said.

"Misperception among obese children is most important," Burke said.

And though it seems logical that parents who more accurately perceive their kids' weight will be more ready to try to change an overweight child's behavior, it may not be that simple, she said.

"It's not clear that if a doctor hammers home that a child is overweight, the parent will have more readiness to help child engage in more healthful behaviors," she said.

"Do you really need to change parental perception first? It may be more effective to promote healthier behaviors among all kids," she said.

Some people mistrust growth charts, she said, but most accept that good health behaviors like eating right and exercising apply to them, Burke said.

Parental perceptions might be changing over time as obesity becomes more common, since people generally judge themselves (and their children) against the people around them, she said.

It is also possible that more parents are unwilling to admit their children are overweight due to the increasing stigma of obesity, Zhang said.

The Division of Nutrition, Physical Activity, and Obesity provides helpful tips to help children maintain a healthy weight and growth charts for interpreting their weight class, available here, he noted.

SOURCE: bit.ly/1ltNBCt Pediatrics, online August 25, 2014