Heterogeneous phenotypes of insulin resistance and its implications for defining metabolic syndrome in Asian Indian adolescents

Objective To assess the phenotypic correlations of insulin resistance with obesity and its relationship with the metabolic syndrome in Asian Indian adolescents. Design and subjects We analyzed clinical, anthropometric (body mass index [BMI], waist circumference [WC]) and laboratory (fasting blood glucose [FBG], lipids and fasting serum insulin) data from 793 subjects (401 males and 392 females) aged 14–19 years randomly selected from Epidemiological Study of Adolescents and Young (ESAY) adults (n = 1447). The percentile cut-offs for 14–19 years age from ESAY cohort were used for defining abnormal values of variables. We devised three sets of definitions of metabolic syndrome by including BMI and fasting insulin levels with other defining variables. Results Nearly 28.9% of adolescents had fasting hyperinsulinemia despite normal values of BMI, WC, FBG, lipids, and blood pressure. Remarkably, NCEP criteria with appropriate percentile cut-off points for Asian Indian adolescents identified metabolic syndrome in only six (0.8%) subjects. Inclusion of both BMI and WC in the definition resulted in increase in the prevalence of metabolic syndrome to 4.3%. With inclusion of hyperinsulinemia, the prevalence of metabolic syndrome increased to 4.2% (from 0.8%) in the modified NCEP definition, 5.2% (from 0.9%) when BMI was substituted for WC, and 10.2 (from 4.3%) when both BMI and WC were included. Conclusions Our data show marked heterogeneity of phenotypes of insulin resistance and poor value of NCEP definition to identify metabolic syndrome. We propose that BMI and fasting insulin should be evaluated in candidate definitions of metabolic syndrome in Asian Indian adolescents.