The ways in which we perceive ourselves may matter more than we realize. In a forthcoming paper from Psychological Science, teens who felt fat at a normal weight ran a greater risk of becoming overweight or obese by the time they were 30.

The paper, which New York Magazine’s Science of Us received ahead of print, used data from the National Longitudinal Study of Adolescent Health; 6,523 people between the ages of 16 and 28 were surveyed. Researchers assessed a participant’s body mass index (BMI) by measuring their height and weight, in addition to asking questions like, “How do you think of yourself in terms of weight?” The focus of the study had to do with participants who perceived themselves as overweight or obese when, in reality, they were considered a normal weight.

After comparing these participant’s answers to those who accurately perceived their weight, researchers found 16-year-olds who feel fat increased their risk of becoming obese in adulthood by 40 percent. In other words, misperception can double as a self-fulfilling prophecy.

Prior research has shown perception affects how we feel about our age, too. A study from JAMA Medicine found older people who felt three or more years younger than their chronological age had a lower death rate compared to those who feel their age — or a year older than their actual age. Similarly, another study from Psychological Science found overcoming negative age stereotypes, such as “spry and old,” improved health outcomes. Researchers said “subjective age is malleable” and to change it influences older adults’ cognition and behavior.

The point is self-perception can carry a significant weight (no pun intended). It is, as written Life Hacker, a necessary component of self-improvement. For normal-weight teens who feel overweight, or for older adults who feel older than they are, Psych Central recommends exercises to boost self-esteem. One of which is a self-esteem inventory — more or a less a list of your strengths and weakness — which is a technique commonly used in cognitive behavioral therapy.

“It can be quite jarring when your vision of yourself is out of sync with the way you're seen by others. Whether it's a physical quality or an aspect of your personality, that feeling that you're not being truly seen is uncomfortable,” Dara Chadwick, author of You’d Be So Pretty If…, said in a column for Psychology Today. “But the thing about perception is that it's incredibly subjective — to perceive, literally, means to ‘know or identify by means of the senses.’Quite simply, we feel what we feel, sometimes in spite of what our eyes alone tell us.”

Source: Sutin A.R., et al. Psychological Science. 2014.