"The trend is very dangerous," said Dr. Jian Zhang, who describes the phenomenon as a vicious cycle.
It's also very complicated. Teenagers suffer through a lot of things, including an acute pressure of appearance. As a result, this is a worry that stems from health concerns, but requires a difficult balance in educating young people without causing or furthering anxiety about body image.
The researchers used data from the National Health and Nutrition Examination Survey, an in-depth study of the nutritional status of adults and children in the United States, which tracked, among other things, the health of nearly 2,000 teenagers between the ages of 12 and 16 in the early 1990s and over 2,500 teenagers in the same age range between 2007 and 2012. As part of the study, participants' body mass index—which is a fairly reliable measure of obesity among children, though less so among adults—was collected, along with the response to this rather straightforward question: "Do you consider yourself to be overweight, underweight, or just about the right weight?"
When the two were juxtaposed—what each adolescent said in response to the question, and what their corresponding BMI said about their weight—Zhang's team noticed a pretty clear trend: Far fewer kids believe that they are overweight today, even though many more of them should.
"Within a short time scale, the likelihood that overweight or obese teens believe that they are overweight declined by almost 30%," said Zhang.
Adolescents, for instance, are 29 percent less likely to correctly perceive themselves as being overweight than they were almost twenty years ago, according to the study's findings. And the drop-off is the most pronounced among younger children—overweight 12-year-olds are almost 40 percent less likely to understand that they are overweight today.
Even after adjusting for factors like race, sex, and socioeconomic status, the change is still stark. In fact, it's rich white kids who have developed the poorest understanding. Zhang points out that that's partly due to the reality that teens from minority groups began with a higher proportion of misperception. But it also reflects how widespread the change is.
The immediate danger resulting from poor self-awareness among overweight children is pretty clear: It's hard enough to lose weight when you know that you should. You can imagine how the the difficulty compounds when you don't—and you're still a child. But that lack of self-awareness among kids is made worse by the fact that mothers and fathers are becoming more oblivious too. A study published last year by Zhang found that parents are significantly less likely to realize that their child is obese than they were twenty years ago.
"The society as a whole is stuck with a vicious cycle," Zhang told Healthday last year. "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."
What's going on? The reason we are not only getting fatter, but also less adept at realizing it, might have to do with a phenomenon sociologists call social comparison theory, which holds that we aren't all that great at comparing ourselves to a static, absolute measure. Instead of judging whether we are overweight from a scientific standpoint, we make the assessment based on the people around us, and those people around us are getting fatter.
Taboo could be a leading factor, too. Zhang himself admits that the obesity pandemic has given rise to a weight loss industry that often has stern things to say about people who need to shed pounds. "Facing harsher messages, more and more overweight and obese adolescents may be increasingly reluctant to admit that they are overweight," the study notes.
And everything might simply be self-perpetuating itself over time. The more kids there are who are obese but don't identify themselves as being obese, the harder it is to establish a common understanding, especially at at younger ages. The same goes for the number of overweight adolescents who aren't willing to admit that they are overweight.
This isn't the first time that our collective weight misperception has been analyzed—the Centers for Disease Control and Protection released a startling report last year, which showed that almost half of America's obese youth don't know they're obese. But it's the rising lack of self-awareness that is arguably what is most troubling.
Nearly a third of children in the U.S. are considered overweight, according to the Food and Research Action Center. Roughly 35 percent of them go on to become obese in adulthood. The United States is, by almost any measure, one of the fattest countries in the developed world. While being overweight doesn't automatically mean that you are unhealthy, the health and economic costs of the American obesity epidemic are well documented.
Solving the problem isn't as simple as telling people that they're overweight. There's too fine a line between promoting health and facilitating body image issues for that to be the case. Just ask the many people out there who already have complicated relationships with how their bodies look, or consider that eating disorders are on the rise, and even among children. It's important to promote self-appreciation, especially in a world where everyone is inundated with unfair standards of beauty.
"We must be very careful when we, as parents, teachers, or health care professionals, make an effort to correct the misperception among teens," said Zhang. "It has to be a pro-health, not anti-obesity, campaign."