Ethnic differences in insulin resistance and body composition in United Kingdom adolescents

CONTEXT: Type 2 diabetes is increasingly recognized in childhood, occurring more frequently in the United Kingdom in South Asians and in girls. South Asian children have been shown to be more insulin resistant than white European children, and girls more insulin resistant than boys. It is not clear how these sex and ethnic differences relate to body composition in childhood. OBJECTIVE: The goal was to evaluate sex and ethnic differences in insulin sensitivity and body composition in healthy adolescents. DESIGN: This was a cross-sectional cohort study. SETTING: This was a community-based study. PARTICIPANTS: One hundred twenty-nine healthy white European and South Asian 14- to 17-yr-old adolescents participated. INTERVENTIONS: Body composition was assessed by anthropometry and dual-energy x-ray absorptiometry, and insulin sensitivity by homeostasis model assessment. MAIN OUTCOME MEASURES: The main outcome measures were body fat percentage and insulin sensitivity. RESULTS: We confirmed that South Asian adolescents were less insulin sensitive than white European adolescents (homeostasis model assessment of insulin sensitivity, 52.4 vs. 58.9%, P <0.05), with a trend toward lower insulin sensitivity in girls. South Asian adolescents had significantly more body fat than white European adolescents (girls, 30.6 vs. 26.0%, P <0.005; boys, 20.8 vs. 14.8%, P <0.001), with more central fat (waist-thigh ratio in girls, 1.36 vs. 1.25, P <0.001; boys, 1.52 vs. 1.42, P <0.001). The sex-ethnic differences in insulin sensitivity were no longer seen when body fat was included as a covariate. CONCLUSIONS: Ethnic differences in insulin sensitivity are associated with ethnic differences in body fat. South Asian adolescents are more insulin resistant, with more body fat than white European adolescents, which may contribute to their increased risk of developing type 2 diabetes.