When researchers recently looked at data on how parents perceive their overweight young children, they learned that 94.9 percent believe the kids’ size to be “just right.” As startling and unsettling as that statistic may be, it had been shown before in smaller populations and wasn’t the worst news out of the study.

More disturbing was what the researchers found when they compared the results with the same survey taken about two decades earlier. Over the years, they realized, the chances of a child “being appropriately perceived by the parents declined by 30%.” African-American and low-income parents had the most inaccurate perceptions.

“We have changed our perceptions of what our weight ideals are,” even among kids aged 2 to 5, who were the subjects of this study, said Dustin T. Duncan, an assistant professor in the Department of Population Health at NYU Langone Medical Center, who led the research. Most parents can no longer tell what a healthy weight looks like, and their doctors aren’t helping them understand, Duncan said.

“If every other child is obese or overweight, you would think your child” is normal as well, he added. (The study also showed that 78.4 percent of parents of obese children believed them to be “just right,” but the study made no comparison to earlier data for that group.)

Instead of focusing on small groups of overweight or obese kids as other studies have, Duncan’s research used a national sample of children and parents surveyed for the National Health and Nutrition Examination Survey between 1988 and 1994, and others questioned for the same survey between 2007 and 2012. Both samples had more than 3,000 children.

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