Validity of self-reported weight and height among 13-14 year old schoolchildren in Israel

Background: Data regarding the validity of self-reported weight and height in adolescents are conflicting. Objectives: To evaluate the validity of self-reported weight and height among 13-14 year old schoolchildren. Methods: We conducted a cross-sectional study of 517 schoolchildren aged 13-14 years and compared self-reported and measured weight and height by gender, population group, parental education and crowdedness. Results: Females under-reported their weight on average by 0.79 ± 5.46 kg (P = 0.03), resulting in underestimation of the body mass index with borderline significance (mean difference 0.28 ± 2.26 kg/m², P = 0.06). Males overreported their height on average by 0.75 ± 5.81 cm (P = 0.03). Children from less crowded homes (≤ 1 person per room) overestimated their height more than children from more crowded homes, resulting in a significant underestimation of BMI (mean difference between reported BMI and measured values was 0.30 ± 2.36 kg/m², P = 0.04). Measured BMI was a significant predictor of the difference between self-reported and measured BMI, adjusted for gender, population group, parents' education, and crowdedness (β = -0.3, P < 0.0001). As a result of this reporting bias, only 54.9% of children with overweight and obesity (BMI ≥ 85th percentile) were classified correctly, while 6.3% of children were wrongly classified as overweight and obese. The largest difference in BMI was observed in obese females (4.40 ± 4.34) followed by overweight females (2.18 ± 1.95) and underweight females (-1.38 ± 1.75). Similar findings were observed for males, where the largest difference was found among obese males (2.83 ± 3.44). Conclusions: Studies based on self-reported weight and height in adolescents may be biased. Attempts should be made to correct this bias, based on the available data for each population.