Self-perception can sometimes work as a kind of self-fulfilling prophecy, according to an upcoming paper in Psychological Science: Namely, believing that you are fat may result in actually becoming fat. Sixteen-year-olds who were at a normal weight but misperceived themselves to be overweight had a 40 percent greater risk of becoming obese before they turned 30, reports Angelina R. Sutin of the Florida State University College of Medicine. (The paper isn’t online yet, but Science of Us got an advance copy.)
Sutin used data from the National Longitudinal Study of Adolescent Health as the basis for her study, focusing on answers from 6,523 people who were surveyed at the ages of 16 and 28. As teenagers, the study participants’ height and weight was measured in the lab in order to assess their body mass index, or BMI, a standard (if controversial) way of assessing healthy weight; they also answered questions like, “How do you think of yourself in terms of weight?” Sutin and her team zeroed in on the adolescents whose BMIs indicated that they were at a normal weight but whose answers indicated that they perceived themselves to be overweight or obese; the researchers compared these participants with the teenagers who accurately perceived their weight.
And sure enough, the researchers found that the teens who’d believed themselves to be fat had a 40 percent greater risk of becoming obese in adulthood when compared to their peers who’d accurately perceived themselves to be normal weight. Sutin explains in her paper that this is likely because teenagers who see themselves as overweight are more likely to engage in unhealthy dieting strategies like fasting or taking laxatives, and these extreme approaches to weight loss have been linked with more weight gain as teenagers mature into adults.
It’s a reminder for those who study obesity and adolescence that it’s not just the already-overweight kids that they need to worry about, Sutin writes, because “self-stigmatization” may be a bigger risk factor for obesity than previously understood. “You become what you believe” is the kind of inspirational mantra that tends to appear overlaid onto nature pictures on Pinterest, but that doesn’t mean there isn’t some truth to it.