Association between Obesity Indices and Insulin Resistance among Healthy Korean Adolescents: The JS High School Study

Objective To investigate whether indices of obesity are associated with insulin resistance in Korean adolescents. Methods This study was conducted as a cross-sectional analysis of 817 healthy adolescents aged 15-16 years without diabetes. Percentiles group of weight-for-height, body mass index (BMI)-for-age, waist circumference (WC)-for-age, and skin fold thickness (SFT)-for-age were based on the 2007 Korean National Growth Charts. Percentiles of waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), and percent body fat were calculated for the study population. Insulin resistance was estimated by homeostatic model assessment (HOMAIR). Logistic regression models were used to estimate odds ratio for insulin resistance according to seven obesity indices. Generalized linear models were used to assess the associations between obesity indices and continuous HOMA-IR levels. Results Sex and age-adjusted odds ratios (95% confidence interval) for insulin resistance, defined as HOMA-IR>2.50, of the 75-94th and >= 95th percentiles of weight-for-height were 3.87 (2.38-6.30) and 11.37 (5.87-22.02), compared to the <50th percentile. Corresponding odds ratios were 3.27 (2.02-5.28) and 11.72 (6.05-22.73) for BMI-for-age, 4.72 (2.82-7.88) and 13.22 (6.42-27.23) for WC-for-age, 3.67 (2.27-5.94) and 13.58 (6.71-27.48) for WHR, 4.78 (2.99-7.67) and 12.84 (6.23-26.46) for WHtR, 2.62 (1.61-4.26) and 6.68 (3.46-12.90) for SFT-for-age, and 2.29 (1.33-4.26) and 10.06 (4.39-23.06) for body fat. These associations were more prominent when insulin resistance was defined as HOMA-IR>3.16 and were stronger in males than in females. Continuous measure of HOMA-IR was significantly associated with body weight, BMI, WC, WHR, WHtR, and SFT in both sexes (p<0.001), and with percent body fat in males only (p<0.001). Conclusion Our findings suggest that obesity indices are positively associated with insulin resistance in apparently healthy adolescents.