[Factors associated with obesity among adolescents]

Obesity during adolescence is considered a strong predictor of adult obesity. The present study assessed the overweight/obesity prevalence and associated factors in middle class adolescents of a school in the city of Niteroi, Rio de Janeiro, Brazil, and evaluated the correlation between body mass index with anthropometric measures of fatness.

The analysis covered 391 students aged from 15 to 17 years. Adolescents had their weight, height, skinfold thickness and upper arm circumference measured at school. A food frequency questionnaire (list of 79 items) and a questionnaire including food habits, parents anthropometric characteristics, physical activity and other factors associated with obesity were filled out by the adolescents at school.

The proportion of overweight individuals among boys (Body Mass Index (BMI) greater than the 90th percentile of the Brazilian population) was 23.9%, whereas the prevalence among girls was 7.2%. The fact of being on a slimming diet was a relevant factor for the prediction of BMI and was 7 times more frequent among girls than among boys. Among boys, being on a diet, absence of breakfast, and family body appearance were positively associated with BMI. Among girls these variables were also significantly associated, whereas age at menarche was negatively associated with BMI. Hours of watching TV/video/video-game was associated with BMI only among boys. The correlation coefficient between BMI and measures of fatness varied from 0.7 to 0.9 for boys, and from 0.8 to 0.90 for girls.

BMI appears to be a good indicator of obesity among adolescents and showed that girls demonstrated an exaggerated preoccupation with body image and stereotyped slim body patterns.