Many parents think their overweight children and healthy, according to a recent study.

Researchers found that more than three-quarters of parents perceived their overweight children as "about the right weight," HealthDay reported. The finding reveals that parents today are "far less capable of realizing when their children are overweight or obese" than in the 80s and early 90s.

Among children aged 6 to 11, obesity has more than doubled -- rising from 7 percent in 1980 to nearly 18 percent in 2012.

"The society as a whole is stuck with a vicious cycle," senior study author Dr. Jian Zhang, an associate professor of epidemiology at Georgia Southern University in Statesboro, told HealthDay. "Parents incorrectly believe their kids are healthy, they are less likely to take action, and so it increases the likelihood that their kids will become even less healthy."

For the study, the research team collected and analyzed data from the U.S. National Health and Nutrition Examination Survey, which has been conducted at regular intervals by the U.S. Centers for Disease Control and Prevention since the early 1960s.

Parents were asked whether they considered their child to be overweight, underweight or just about the right weight. The child's weight and height were then measured to calculate the body-mass index (BMI).

Parents surveyed between 1988 and 1994 correctly perceived about 51 percent of the time that their child was overweight or obese. Between 2005 and 2010, that number slipped to 44 percent.

Zhang said medical definitions of obesity and overweight have become "overly complicated," making it difficult for parents to accurately apply the standard to their child, HealthDay reported.

"The recommendation developed by the CDC is fairly complicated, and it can be very hard for parents to understand that," he said.

Zhang added that parents could also be reluctant to label their child as overweight or obese because of the stigmatization of the term.