Comparison of Three International Definitions for Overweight and Obesity in a Population of Adolescents in Greece

Background: Early diagnosis of obesity in adolescents is crucial for the prevention of severe health consequences. Different criteria for the diagnosis of obesity may lead to variations in prevalence. We aimed to compare the three most widely used international definitions (by WHO, IOTF and CDC) for overweight/obesity in adolescents in Northwestern Greece. Methods: A total of 403 adolescents aged 10–17 years were included. Agreement metrics and assessment of marginal heterogeneity and asymmetry were used for the comparison of the definitions. Results: In the total population, high agreement was observed among all definitions (Krippendorff’s alpha: 0.931, 95% CI 0.913–0.949). However, there was significant marginal heterogeneity (p < 0.001) and asymmetry (p < 0.001) for each pairwise comparison. WHO definition consistently yielded higher prevalence of obesity (WHO: 23.1%, IOTF: 15.4%, CDC: 21.6%). There were no significant differences in agreement (p = 0.247 for the comparison) between males and females, with more prominent marginal heterogeneity and asymmetry in males. Agreement among definitions was numerically lower in young adolescents aged < 14 years versus older ones (alpha: 0.919 vs. 0.953, p = 0.082), and systematic bias (p < 0.001) and asymmetry (p < 0.001) were present only in young adolescents without any significant difference in older ones. Conclusions: Although agreement was very high among definitions, they are not interchangeable, yielding different prevalence rates, particularly in young adolescents. IOTF criteria resulted in a reduced diagnosis of obesity and could lead to undertreatment; in contrast, WHO and CDC criteria may lead to overdiagnosis in our population. Caution is required when interpreting international criteria for overweight/obesity in various populations.