Bias in self-reported height and weight in preadolescents.

Objective: To examine the validity of self-reported height and weight and factors related to misreporting in preadolescents. The accuracy of screening for underweight (thinness), overweight, and obesity using self-reported data was also tested.

Methods: Self-reported height and weight was administered and then measured in 798 fourth graders age 8 to 11 years. Body mass index (BMI) was calculated from self-reported and measured data and BMI categories were determined using international age- and sex-specific BMI criteria.

Results: Preadolescents overestimated their height by 0.54 ± 5.17 cm and underreported their weight by 0.80 ± 3.09 kg. BMI derived from self-reported data was underestimated by 0.47 ± 1.79 kg/m². Measured BMI category was an important independent predictor of bias in self-reported weight and BMI. Children who were overweight or obese underestimated their weight and BMI to a greater degree compared with normal weight/underweight children. The influence of sociodemographic factors on bias in self-reported values was relatively small. Approximately 15% of children were misclassified in BMI categories when self-reported data were used, especially in the underweight (thinness) and obese category.

Conclusions: Children age 8 to 11 years were not able to accurately estimate their actual height and weight, leading to erroneous estimating rates of their weight status.