As national obesity rates have risen in the last 20 years, overweight and obese adolescents are now less likely to accurately perceive their body weight, according to a recent study at Georgia Southern University.

The study, “More Overweight Adolescents Think They Are Just Fine,” is being published in the upcoming issue of the American Journal of Preventative Medicine and is part of a series of research initiatives led by Dr. Jian Zhang, associate professor of epidemiology in the Jiann-Ping Hsu College of Public Health.

While previous papers have focused on the parents of preschoolers and school-age children, Zhang said this study focuses on the adolescents themselves, both because of their growing independence from parents and because of a diminishing likelihood they will outgrow their obesity as adults.

“It’s estimated that about a third of obese preschoolers and half of obese school-aged children — including adolescents — will become obese adults,” he said. “Adolescents with accurate self-perceptions of their body weight have greater readiness to make weight-related behavioral changes and are more effective in making the changes. By contrast, overweight adolescents who do not perceive their weight status properly are less likely to desire weight loss and are more likely to have a poor diet.”

Zhang and researchers from Georgia Southern and Fudan University in Shanghai compared data from adolescents ages 12-16 who participated in the National Health and Nutrition Examination Survey in 1988-1994 and in 2007-2012. Respondents were asked if they thought they were overweight, underweight or just about the right weight.

The study revealed that overweight or obese adolescents from the most recent survey were 30 percent less likely to accurately perceive their body weight compared to adolescents from the earlier survey.

The researchers suggest that a combination of issues may be the reason for this change in perception. As the prevalence of obesity has more than doubled in adolescents during the last 20 years, Zhang believes our socially accepted standards for “normal weight” may be shifting accordingly.

In addition, researchers pointed to social-comparison theory as a possible explanation. According to the theory, individuals compare themselves to others, rather than to some scientific standard such as the Body Mass Index.

“In the wake of an obesity pandemic, a teenager is more likely to compare his or her body size to peers or friends, or anyone she or he sees daily,” said Andrew Hansen, Dr.P.H., assistant professor of community-health behavior and education and spokesman for the research group. “Teenagers are less likely to use growth charts and biologic tools to measure their weight, but are more likely to socially compare or associate their weight to what they feel is normal.”

Because of these factors, Zhang says exploring new strategies to correct these body-weight misperceptions is more urgent than ever, and that parents are a key factor.

“As parents, we need to proactively create a conducive family environment to engage kids with a healthy lifestyle — clearly let our teens know that we care,” he said. “It is also crucial that we proactively discuss weight issues with doctors to make sure youths are on a healthy growth track.”

Zhang says parents also should serve as role models, watching their own weight and focusing on healthy lifestyles instead of weight control to protect their teens’ attitude about body image.

“This doesn’t have to be an anti-obesity campaign,” Hansen said. “This can be a pro-health campaign.”