Does Thinking You are Fatter Make You Fatter

Adolescence is a vulnerable period for the onset of body image dissatisfaction and eating disorders. Many adolescents misperceive their body size; it is not uncommon for normal weight* adolescents to categorize themselves as overweight. What is the effect of this misperception of body size? Compared with normal weight teens who accurately perceive their weight, those who misperceive their weight as overweight are more likely to diet for weight loss, use extreme weight loss measures such as diet pills, laxatives, vomiting, or not eating for 24 hours or more, exercise more, spend more time using electronics (“screen time”), and are more prone to overeating. Many of these behaviors are linked with development of obesity. In “Body Weight Misperception in Adolescence and Incident Obesity in Young Adulthood” researchers investigated if normal weight teens that misperceived themselves as overweight were more likely to develop obesity over a 12-year period.

The researchers used data from the National Longitudinal Study of Adolescent Health to examine over 6,500 participants who were on average 16 years old at the time of initial assessment and on average 29 years old at the time of follow-up. Data on body mass index was compared with participants’ responses to the question: “How do you think of yourself in terms of weight?” Participants responded on a scale from 1-5, 1 = very underweight and 5 = very overweight. Results indicated that normal weight adolescents who misperceived themselves as overweight were 1.41 times more likely to become obese by early adulthood than normal weight peers who accurately perceived themselves. This effect was independent of baseline BMI. There was a significant effect of gender; boys who misperceived themselves were 1.89 times more likely to become obese than boys who accurately perceived themselves while girls who misperceived themselves were 1.29 times more likely to become obese than girls who accurately perceived themselves.

The authors conclude that misperception of weight in adolescence is associated with obesity in early adulthood. Adolescents who perceive themselves as overweight are more likely to engage in unhealthy weight control behaviors (such as extreme dieting) that are linked with long-term weight gain. Internalized weight stigma may also play a role in the development of obesity in this group. There is growing evidence that social stigma of body weight is associated with development of obesity; this study suggests a self-imposed label of overweight can result in just as powerful outcomes. This study underscores the importance of addressing body image and disordered eating in adolescents of all shapes and sizes, including those in the normal weight category.

*The authors of the study use the terms normal weight, overweight, and obese to describe classifications according to Body Mass Index. For consistency, I use the same language in this review. For a discussion on the language that we use to talk about fat, please see my blog post “Is Fat The New F-Word?”

Read more of Dr. Conason’s blog posts in Eating Mindfully on Psychology Today