TUESDAY, Jan. 8 (HealthDay News) -- Teenaged girls who believed they were lower on the social ladder were more likely to put on extra pounds, U.S. researchers report.

The researchers, led by Adina R. Lemeshow of the Harvard School of Public Health in Boston and the New York City Department of Health and Mental Hygiene, Bureau of Tobacco Control, analyzed questionnaires completed by 4,446 girls, aged 12 to 18, in 1999.

The questionnaire collected information about height, weight, television viewing habits, diet and other factors, including the girls' perceived social standing at school.

Girls who said they were at four or below (lowest) on a 10-point scale of social standing were more likely to put on extra weight over the next two years than those who said they had a standing of five or higher.

The average body-mass index (BMI) among all the girls was 20.8 in 1999 and 22.1 in 2001. During those two years, 520 of the girls (11.7 percent) had at least a two-unit increase in BMI.

"After adjusting for age, race/ethnicity, baseline BMI, diet, television viewing, depression, global and social self-esteem, menarche, height growth, mother's BMI and pretax household income, adolescent girls who placed themselves on the low end of the school subjective social status scale had 69 percent increased odds of having a two-unit increase in BMI during the next two years compared with other girls," the study authors wrote.

The findings were published in the January issue of the Archives of Pediatrics & Adolescent Medicine.

"It is important that researchers consider physical, behavioral, environmental and socioemotional factors that might contribute to the rising prevalence of overweight in adolescents," the researchers concluded.

"Previous research suggests that emotional factors such as depression and low self-esteem and self-perception contribute to the burden of overweight in adolescents. Our study contributes to this body of literature in that, to our knowledge, it is the first to prospectively evaluate the relationship between subjective social status in the school community and change in BMI, and our findings suggest that low school subjective social status may be an important contributor to increases in BMI in girls over time."

According to background information in the study, the percentage of American teen girls classified as overweight increased from 14 percent to 16 percent between 1999 and 2004.

Another study in the same issue of the Archives of Pediatrics & Adolescent Medicine, looked at 3,345 American teens in grades 8 to 12 and found that those who were physically active at school and outside of school were less likely to be overweight when they were young adults.

For every day per week that teens were physically active at school, their risk of being overweight as young adults was reduced by 5 percent, the study said. Teens who had physical education five days a week were 28 percent less likely to be overweight as young adults.

"Regarding extracurricular physical activities, the likelihood of being an overweight adult was reduced most (i.e., 48 percent) by performing certain wheel-related activities (i.e. in-line skating, roller skating, skateboarding or bicycling) more than four times a week," the study authors wrote.

About 16 percent of American teens are overweight or obese, and 85 percent of obese adolescents become obese adults, according to background information in the study.

More information

The Nemours Foundation has more about teens and healthy weight.

-- Robert Preidt

SOURCE: JAMA/Archives journals, news release, Jan. 7, 2008

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