Validity of self-reported weight and height in Austrian adults: Sociodemographic determinants and consequences for the classification of BMI categories

Abstract

Objective Epidemiological studies have shown that adults tend to underestimate their weight and overestimate their height. This may lead to a misclassification of their BMI in studies based on self-reported data. The aim of the present study was to assess the validity of self-reported weight and height in Austrian adults. Design Data on weight, height, health behaviour and sociodemographic characteristics of adults were collected in a standardized procedure via a self-filling questionnaire and a medical examination including measurements of weight and height. Setting A publicly accessible out-patient clinic in southern Austria. Subjects Austrian residents (n 473) aged 18 years and older who attended a health check participated in the study. Results The mean difference between reported and measured BMI was not significant in younger adults (<35 years: mean difference -0.21 kg/m 2; P < 0.08) but increased significantly with age (≥55 years: mean difference -0.68 kg/m 2; P < 0.001). The prevalence of normal weight (BMI = 18.5-24.9 kg/m 2) and overweight (BMI = 25.0-29.9 kg/m 2) was overestimated based on the self-reported data on BMI, while that for underweight (BMI < 18.5 kg/m 2) and obesity (BMI ≥ 30.0 kg/m 2) was underestimated (P < 0.001). The self-reported data showed an obesity prevalence of 12.5 %, while measurement showed a prevalence of 15.4 % (P < 0.001). Conclusions Our results indicate that prevalence rates of obesity are probably underestimated for Austrian adults when using self-reported weight and height information. The deviations from the measured data clearly increased with age. Analyses based on self-reported data should therefore be adjusted for the age dependency of the validity. © The Authors 2011.