[Validation of self-reported weight and height university population and factors associated with differences between self reported and measured antropometrics].

INTRODUCTION: Obesity is an important public health problem related to a higher risk of death from chronic degenerative diseases such as diabetes, cardiovascular diseases and several types of cancer. In epidemiological studies of big sample size, only self-reported weight and height can be collected for feasibility reasons and body mass index (BMI) estimates may be questioned.
OBJECTIVES: In this study we compare self-reported and measured weight, height and BMI in a mostly young population of university students, and explore factors associated with discrepancies between self-reported and measured data.
METHODS: In the period 2006-2012, 628 University students (476 women) from health sciences subject gave consent to participate in this study. Self-reported weight and height were collected by questionnaire and compared with weight and height measured afterward in health exams wearing light clothes and using standardized protocols. The validity of self-reported anthropometric estimates was explored by correlation coefficients and sensitivity, specificity, predictive values and kappa to detect measured overweight/obesity (BMI ≥ 25 kg/m²). Multiple linear regression was used to explore the factors related to the discrepancies between self-reported and measured data.
RESULTS: The mean of self-reported weight, height and BMI was 62.5 kg, 167.6 cm and 22.1 kg/m² and the mean of measured data was 62.6 kg, 167.4 cm y 22.2 kg/m² respectively. Correlations between self-reported and measured data were r = 0.97 for weight, 0.96 for height and 0.95 for BMI. The sensitivity to detect overweight (IMC ≥ 25 kg/m²) using self-reported data was 81.0%, the specificity was 98.5%, the predictive value was 90.6% and the kappa index was 0.75. The discrepancy between measured and self-reported weight, height and BMI was associated with a higher age, and a higher sleeping time was also associated to discrepancies in self-reported and measured height.
CONCLUSIONS: Despite the self-reported weight and BMI may underestimate the true weight and BMI, and self-reported height overestimate, the validity of self-reported anthropometric measures is adequate to use be used in epidemiological studies among young people with a high educational level.