The “True” Prevalence of Obesity:A comparison of objective weight and height measures versus self-reported and calibrated data

Abstract

A regression model that describes the relationship between body mass index (BMI, kg/m²) based on self-reported weight and height, and body mass index based on objective measurements, makes it possible to calibrate the BMI based on self-reports. Calibrated data on prevalence of obesity are much higher than those calculated from self-reports. The aim of the present study was to evaluate which estimates of prevalence of obesity agreed better with objective values, those based on self-reported data or those based on calibrated BMIs. Results from two different representative samples of the same Swedish d county were compared. Objective values were based on measurements of 2190 men and 1511 women (25—65 years of age) in 1977. Self-reports from 148 men and 147 women (25—64 years of age) were derived from the ULF-study, 1980—81 (Survey on Living Conditions) and then calibrated. The comparison demonstrated that calibrated data, compared with self-reports, are much closer to objective values. There was a striking agreement between objective (14.0%) and calibrated (13.6%) estimates of prevalence of women with BMI > 30.0 kg/m², in contrast to the underestimation by self-reports (8.1%). The calibration method was reliable for the evaluation of the “true” prevalence of obesity in population studies.