A comparison of international references for the assessment of child and adolescent overweight and obesity in different populations

Objective: To compare different references assessing child and adolescent overweight and obesity in different populations. Design: Comparison cross-sectional study. Setting: The United States, Russia, China. Subjects: A total of 6108 American, 6883 Russian and 3014 Chinese children aged 6-18 y. Investigation: Using nationwide survey data from the USA (NHANES III, 1988-1994), Russia (1992), and China (1991), we compared three references: (1) the International Obesity Task Force (IOTF) reference, sex-age-specific body mass index (BMI) cut-offs that correspond to BMIs of 25 for overweight and 30 for obesity at age 18; (2) the World Health Organization (WHO) reference-BMI 85th percentiles for overweight in adolescents (10 - 19 y) and weight-for-height Z-scores for obesity in children under 10; (3) a USA reference-BMI 85th and 95th percentiles to classify overweight and obesity, respectively. Results: Using the IOTF reference and 85th BMI percentiles, overweight prevalence was 6.4 and 6.5% in China, 15.7 and 15.0% in Russia, and 25.5 and 24.4% in the USA, respectively. Notable differences existed for several ages. Kappa ( = 0.84 - 0.98) indicated an excellent agreement between the two references in general, although they varied by sex-age groupings and countries. Overweight prevalence was twice as high in children (6 - 9 y) than in adolescents (10 - 18 y) in China and Russia, but was similar in the USA. Estimates of obesity prevalence using these three references varied substantially. Conclusions: The references examined produce similar estimates of overall overweight prevalence but different estimates for obesity. One should be cautious when comparing results based on different references.