Obese white teenage girls who lose weight may benefit physically, but the weight change does not guarantee they are going to feel better about themselves, according to a Purdue University study.

"We found that obese black and white teenage girls who transitioned out of obesity continued to see themselves as fat, despite changes in their relative body mass," said Sarah A. Mustillo, an associate professor of sociology who studies obesity in childhood and adolescence. "Further, obese white girls had lower self-esteem than their normal-weight peers and their self-esteem remained flat even as they transitioned out of obesity."

The Centers for Disease Control and Prevention reports that about 17 percent of American children ages 2-19 are obese.

"If the current national movement to end childhood obesity is successful, we can anticipate many young people moving from obese into the normal weight range, which will result in better physical health," Mustillo said. "I wanted to know if the same thing would happen for psychological health. Girls often struggle with self-esteem anyway during adolescence and, therefore, it is troubling to find that the negative effects of larger body size can outlive the obesity itself."

The study, based on data from the National Heart, Lung and Blood Institute Growth and Health Study, is in the current issue of the Journal of Health and Social Behavior. The health and weight of more than 2,000 black and white girls was followed for 10 years starting at ages 9 to 10 as part of the national study. For this study, the girls were separated into one of three groups -- normal weight, transitioned out of obesity and chronically obese -- based on their body mass trends during the 10-year period.

There was a difference in self-esteem levels between races. Self-esteem for black girls transitioning from the obese to the normal range did rebound; however, both races continued to have negative body perceptions.

"The self-esteem for black girls was lower overall to begin with, but for those who moved into the normal weight range, self-esteem increased more than it did for any other group of girls," Mustillo said. "We would like to look at this at more closely to understand how subcultural norms influence this process.

"We did not show that self-esteem stayed flat because girls continued to see themselves as heavy, but just that they happened at the same time," she said. "Even so, providing mental health assistance during the weight loss process could be a benefit. Understanding and addressing body image, identity and self-esteem issues could ultimately help keep the weight off. Why keep dieting and exercising if you are still going to see yourself as fat?"

More research is needed to understand why girls feel this way, but Mustillo, who focuses on the trajectories of obesity in adolescence, said the feeling of lesser self-worth might be difficult to shake because society is full of negative stereotypes and messages about obesity.

"Studies show that children internalize stereotypes and negative perceptions of obese people before they ever become obese themselves, so when they do enter that stigmatized state, it affects their sense of self-worth," she said. "Then, whether they are gaining or losing weight, the negative message they have internalized and feelings of worthless may stick with them."

Another aspect of this study to consider is that the data set used is from the 1980s and '90s, and doesn't reflect today's higher obesity rates.

"Obesity is more common today than it was 10 to 20 years ago, so perhaps it is becoming less stigmatized," she said. "Or, will the increase of anti-obesity campaigns counteract any greater acceptance?"

Mustillo is continuing to study this issue by identifying the specific vulnerable periods in adolescence when the stigma of obesity affects young people's mental health more. Her work is supported by Purdue's Department of Sociology in the College of Liberal Arts. Her co-authors are Kimber L. Hendrix, a Purdue doctoral student in sociology, and Markus H. Shaffer, an assistant professor of sociology at the University of Toronto.