Validity of self-reported height and weight and predictors of bias in adolescents.

PURPOSE: The purpose of this study was to assess the validity of self-reported height and weight, the accuracy of screening for overweight and obesity using these data, and the predictors of bias in self-reported height and weight in adolescents.
METHOD: The Health Behavior in School-Aged Children (HBSC) survey was used to assess self-reported and measured height and weight in a community sample of 418 students in year 11 from 21 secondary schools in Wales. Participants also provided self-report data on dieting and body perception.
RESULTS: Self-reported and measured height and weight were highly correlated but a bias of underreporting of body weight by an average of .52 kg contributed to underestimation of the prevalence of overweight and obesity. Based on self-report data, 13.9% of the sample was identified as overweight and 2.8% was identified as obese, but measured data showed rates of 18.7% and 4.4%, respectively. Overweight and obese participants showed greater bias and variability in self-reported weight than normal/underweight participants. Body mass index (BMI) and body dissatisfaction predicted bias in self-reported weight.
CONCLUSION: Self-report bias had significant consequences for the accuracy of a screen for overweight and obesity. Actual and perceived body size each contribute to underreporting body weight. Self-reports will remain an important health surveillance tool but should not be relied on exclusively to detect weight problems. Accuracy checks of self-report data may improve surveys of weight problems in young people.