[Measured weight, self-perceived weight, and associated factors in adolescents]

To compare weight self-perception and nutritional status based on objective measurements of weight, height, and skin folds in adolescents, and to evaluate factors associated with disagreement between these measures.

The sample included the 1993 birth cohort from the city of Pelotas, Brazil, who were interviewed at home in 2004 and 2005. The study outcome resulted from the comparison between nutritional status and the weight self-perception of adolescents, and was divided into three categories: underestimation, agreement, and overestimation. The explanatory variables were sex, skin color, accumulated goods index, physical activity, eating habits, discrimination, dieting, feeling of well-being, and opinion of the adolescent concerning the perception of his/her parents regarding the adolescent's weight. Multivariate logistic regression was used for statistical analysis.

A total of 4 452 interviews were conducted (87.5% of original cohort). Mean age was 11 years. The analysis of nutritional status revealed that 7.1% were underweight, 69.8% normal weight, 11.6% overweight, and 11.6% obese. The analysis of self-perceived weight revealed that 19% saw themselves as thin or very thin, 56% believed their weight was normal, and 25% saw themselves as fat or very fat. Global agreement between weight self-perception and nutritional status was 65% (kappa = 0.36). Weight underestimation occurred in 24.9% of boys vs. 20.3% of girls. Overestimation occurred in 15.8% of girls vs. 8.5% of boys.

Girls tended to overestimate their weight, and boys, to underestimate it. There was a strong association between the opinion of adolescents concerning their parents' view of the adolescent's body and self-perceived weight.