Teens who incorrectly think they're on the heavy side are more likely to be obese as young adults, according to a new study.

The last three decades have brought an alarming rise in childhood obesity. Much of society's attention has centered on kids who've already put on a few too many pounds, but that overlooks one important group of kids: teens who think they're more overweight than they actually are. Turns out, their misperceptions greatly increase the chances they'll be obese as young adults.

Researchers who've studied obesity know there are a number of psychological factors that can put people at risk for obesity, among them weight discrimination. In a 2013 study, for example, Angelina Sutin and Antonio Terracciano of Florida State University found that both normal and overweight adults who felt they'd been treated unfairly because of their weight were more likely to become obese than others. Likely, the psychologists argued, that's because the stress and stigmatization of obesity—jokes, job discrimination, even physical attacks—led to depression, overeating, and less exercise.

After the 2013 study was published, "we started wondering whether the stigmatization had to be from other people, or would there be a similar effect of self-stigmatization?" Sutin writes in an email. In other words, if people thought they themselves were overweight, could that misperception, and the negative emotions associated with it, be enough to lead to obesity? In a word, yes, according to results they published last week in Psychological Science.

"Our findings suggest that it is important to pay attention to perceptions of weight, not only actual weight status—misperceptions can have similar consequences and such discrepancies should be taken seriously."

To find answers, Sutin and Terracciano turned to the National Longitudinal Study of Adolescent Health, better known as Add Health. The survey recruits children and teens and tracks their health and well-being into young adulthood. For Sutin and Terracciano's purposes, it asks a key question: "How do you think of yourselves in terms of weight?" Sutin and Terraciano collected responses from 6,523 normal-weight teens, aged 16 on average, and focused their attention on those who'd answered that they were either normal, somewhat overweight, or very overweight.

Normal-weight kids who thought they were overweight, Sutin and Terracciano found, were much more likely to become obese by young adulthood, compared with those who'd thought their weight was normal. Those who thought they were overweight as teens were about 40 percent more likely to be obese when Add Health researchers followed up with them in their late twenties, though the effect was much greater for men compared with women. Normal-weight girls who thought they were overweight had roughly 30 percent higher odds of becoming obese compared with others. For boys, meanwhile, the odds of becoming obese jumped nearly 90 percent if they thought they were overweight as teens.

"Our findings suggest that it is important to pay attention to perceptions of weight, not only actual weight status—misperceptions can have similar consequences and such discrepancies should be taken seriously," Sutin writes. "At the same time, we need to be careful in how weight is discussed with adolescents so as not to lead them to develop misperceptions," she writes.

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