Visceral adiposity is closely correlated with neck circumference and represents a significant indicator of insulin resistance in WHO grade III obesity

OBJECTIVE: Although associations between visceral adiposity (intra-abdominal fat mass) and insulin resistance are well established, previous data include few subjects with WHO grade III obesity [body mass index (BMI) > 40 kg/m(2)]. We have investigated the relationship between visceral adiposity and insulin resistance using computed tomography (CT)-quantified fat mass and the homeostasis model assessment for insulin resistance (HOMA-IR) in patients with severe obesity. PATIENTS AND METHODS: Eighteen nondiabetic subjects with BMI > 40 kg/m(2) were recruited. BMI, and waist, hip and neck circumferences were measured. Fasting plasma insulin and glucose were measured to calculate HOMA-IR. A single slice CT scan was taken at L4 and visceral and abdominal subcutaneous adipose tissue (VAT and ASAT, respectively) quantified using 'SliceOmatic' image analysis software. RESULTS: A close correlation was demonstrated between VAT and HOMA-IR (r(2) = 0.46, P = 0.002), whereas ASAT showed no relationship. Neck circumference correlated with both VAT (r(2) = 0.67, P < 0.0001) and HOMA-IR (r(2) = 0.35, P = 0.01). Waist circumference only correlated significantly with VAT (r(2) = 0.25, P = 0.03). CONCLUSIONS: Visceral adiposity remains a strongly significant indicator of insulin resistance in WHO grade III obesity. Neck circumference surpasses other anthropometric measurements as a powerful marker of both VAT and insulin resistance.