Self-reported versus measured body height and weight in Polish adult men: the risk of underestimating obesity rates.

BACKGROUND In some epidemiological studies, self-reported height and weight are often used to save time and money. Self-reported height and weight are commonly used to assess the prevalence of obesity. The aim of this study was to assess the differences between self-reported and measured height and weight in adult men, and to determine how the accuracy of self-reported data depended on age and education. The prevalence of obesity was also calculated based both on self-reported and measured data. MATERIAL AND METHODS Data were collected during two population studies carried out in Wroclaw in 2010. One study included 1,194 19-year-old males who reported for the health examination mandated by the National Conscription Board (younger group). The other group included 355 men between 35 and 80 years old who reported for a ten-year follow-up (older group). Data were analyzed separately for both age groups. RESULTS Both younger and older subjects overestimated their height by 1.4 cm and 1.0 cm (1.4 cm, 95 % CI: 1.26, 1.51, and 1.0 cm, 95 % CI: 0.85, 1.26, respectively). On average, younger subjects overestimated their weight by 0.7 kilograms (95 % CI: 0.55, 0.92), whereas older subjects underestimated their weight by 0.9 kilograms (95 % CI: -1.15, -0.48). The lower the level of education, the more the subjects overestimated their height. CONCLUSIONS Adult men systematically overestimate their height and underestimate their weight. The magnitude of the inaccuracy depends on level of education. When self-reported data are used, the prevalence of obesity is generally underestimated. Using self-reported data to calculate BMI can lead to a substantial underestimation of the proportion of underweight and obese individuals in a population. Finally, using self-reported values for height in studies on social inequality may lead to false conclusions. Background: In some epidemiological studies, self-reported height and weight are often used to save time and money. Self-reported height and weight are commonly used to assess the prevalence of obesity. The aim of this study was to assess the differences between self-reported and measured height and weight in adult men, and to determine how the accuracy of self-reported data depended on age and education. The prevalence of obesity was also calculated based both on self-reported and measured data. Material and methods: Data were collected during two population studies carried out in Wroclaw in 2010. One study included 1,194 19-year-old males who reported for the health examination mandated by the National Conscription Board (younger group). The other group included 355 men between 35 and 80 years old who reported for a ten-year follow-up (older group). Data were analyzed separately for both age groups. Results: Both younger and older subjects overestimated their height by 1.4 cm and 1.0 cm (1.4 cm, 95 %CI: 1.26, 1.51, and 1.0 cm, 95 %CI: 0.85, 1.26, respectively). On average, younger subjects overestimated their weight by 0.7 kilograms (95 %CI: 0.55, 0.92), whereas older subjects underestimated their weight by 0.9 kilograms (95 %CI: –1.15, –0.48). The lower the level of education, the more the subjects overestimated their height. Conclusions: Adult men systematically overestimate their height and underestimate their weight. The magnitude of the inaccuracy depends on level of education. When self-reported data are used, the prevalence of obesity is generally underestimated. Using self-reported data to calculate BMI can lead to a substantial underestimation of the proportion of underweight and obese individuals in a population. Finally, using self-reported values for height in studies on social inequality may lead to false conclusions.