Association of Visceral Adipose Tissue and Insulin Resistance with Incident Metabolic Syndrome Independent of Obesity Status: The IRAS Family Study.

OBJECTIVE: Although increasing evidence suggests that visceral adipose tissue (VAT) is a major underlying cause of metabolic syndrome (MetS), few studies have measured VAT at multiple time points in diverse populations. VAT and insulin resistance were hypothesized to differ by MetS status within BMI category in the Insulin Resistance Atherosclerosis Study (IRAS) Family Study and, further, that baseline VAT and insulin resistance and increases over time are associated with incident MetS. METHODS: Generalized estimating equations were used for differences in body fat distribution and insulin resistance by MetS status. Mixed effects logistic regression was used for the association of baseline and change in adiposity and insulin resistance with incident MetS across 5 years, adjusted for age, sex, race/ethnicity, and family correlation. RESULTS: VAT and insulin sensitivity differed significantly by MetS status and BMI category at baseline. VAT and homeostatic model assessment of insulin resistance (HOMA-IR) at baseline (VAT odds ratio [OR] = 1.16 [95% CI: 1.12-2.31]; HOMA-IR OR = 1.85 [95% CI: 1.32-2.58]) and increases over time (VAT OR = 1.55 [95% CI: 1.22-1.98]; HOMA-IR OR = 3.23 [95% CI: 2.20-4.73]) were associated with incident MetS independent of BMI category. CONCLUSIONS: Differing levels of VAT may be driving metabolic heterogeneity within BMI categories. Both overall and abdominal obesity (VAT) may play a role in the development of MetS. Increased VAT over time contributed additional risk.