Accuracy of teen and parental reports of obesity and body mass index

Objectives. Adolescent obesity is becoming an increasing public health problem. This study determines: 1) differences in teen and parental report of obesity, 2) amount of misclassification using body mass index (BMI) from self-reported versus measured height and weight as an indicator of obesity, and 3) whether misclassification varies by gender and socioeconomic status. Design. Weighted data from 15 483 baseline (T1) youth and parental interviews from the National Longitudinal Study of Adolescent Health were used. Seventy-four percent of teens were reinterviewed 1 year later (T2). Parents reported socioeconomic status indicators and whether their teen was obese. Teens reported height, weight, and weight perception. BMI was calculated from both self-reported height and weight at T1 and T2 and from measured height and weight at T2. Those with a BMI greater than or equal to 95% corrected for age and gender were considered obese. Results. At T1, nearly one half of teens (47%) reporting they were very overweight were not obese by BMI. For teens obese by BMI, 19.6% were reported to be obese by both parent and teen, 6.4% by teen only, 29.9% by parent only, and 44.2% by neither teen nor parent. For those with persistent obesity, teen and/or parental report failed to identify more than one third (34%) as obese; 23.4% were identified by both teen and parent report, 5.4% by teen report only, and 37.2% by parent only. At T2, the correlation between BMI calculated from self-reported versus measured height and weight for the overall population was very strong (r = .92). Specificity of obesity status based on self-reported BMI, compared with obesity status based on measured BMI was .996; sensitivity, .722; positive predictive value, .860; and negative predictive value, .978. Overall, 3.8% of teens were misclassified using self-report measures. Girls were no more likely than boys to be misclassified as obese using BMI from self-reported height and weight. Conclusions. Parental report is a better indicator of obesity than teen report of weight status, but parental and teen reports are both poor predictors of adolescent obesity. Using BMI based on self-reported height and weight correctly classified 96% as to obesity status. Thus, studies can use self-reported height and weight to understand teen obesity and its correlates/sequelae.