Validity of self-reported weight, height and BMI in Italian adolescents for assessing prevalence of overweight/obesity

Abstract

Abstract Background/Objectives: Data regarding the validity of self-reported weight and height in adolescents to calculate Body Mass Index (BMI) and determine the prevalence of obesity are conflicting. The aim of the study was to evaluate the validity of self-reported weight and height in the assessment of overweight/obesity prevalence in a sample of Italian adolescents. Subject/Methods: A representative cluster sample of 369 adolescents of the second class of secondary schools in the Lazio region was investigated. Weight and height were both self-reported and measured. BMI was calculated from both self-reported and measured values. Data were analysed using Paired-sample t-test, Student’s t test, Bland-Altman plots and Kappa Cohen’s statistics. Results: The adolescents ‘self-reported weights were underestimated; their heights were overestimated, and their resultant BMI was underestimated. The mean differences were - 0.3±3.7 kg (95% CI -0.68 to 0.08; p 0.116) for weight, 1.2±2.9 cm (95% CI 0.89 to 1.48; p 0.000) for height and 0.4±1.5 kg/m2 ( 95% CI -0.58 to -0.27; p 0.000) for BMI. The prevalence of overweight/obesity was 18.9% based on self-reported data (24.0% for males and 15.0% for females) and 23.3% by measured data (30.2% for males and 17.9% for females). Conclusion: Self-reported weight and height, very useful to simplify large-scale investigations, should be used with caution in Italian adolescents, because they could lead to erroneous estimating rates of overweight and obesity in this population. Introduction