Abdominal fat index by ultrasound does not estimate the metabolic risk factors of cardiovascular disease better than waist circumference in severe obesity

Objective: To evaluate by ultrasound the ratio between preperitoneal (P) and subcutaneous (S) fat (AFI), in quantifying the cardiovascular risk in 258 obese patients (BMI 41.2±6.3 kg/m²; age 45.1 ± 13.6 years). Research methods and procedures: Glucose, insulin, lipid profile, uric acid and fibrinogen were measured. HOMA-IR, waist girth, AFI and quartiles of BMI were calculated. Results: AFI lowered with increasing BMI and showed a positive correlation with TGL (r = 0.37, P < 0.01) and uric acid (r = 0.40, P < 0.001) in the 1^st quartile of BMI (30.2-36.4) and a negative correlation with HDL (r = -0.32, P < 0.001) in the 3^rd quartile (40.6-45.1). When BMI exceeded the value of 45.2 kg/m² these correlations were no longer significant. In all subjects S correlated positively with uric acid (r = 0.64, P < 0.001), and negatively with HOMA-IR (r = -0.41, P < 0.001) and TGL (r = -0.35, P = 0.02); P correlated positively with CHOL (r = 0.48, P = 0.04) and TGL (r = 0.33, P = 0.03), and negatively with HDL (r = -0.46, P = 0.03). Waist girth showed more significant correlations than AFI in the lower quartiles of BMI, but not at the highest one. Discussion: AFI, P and S, as waist girth do not seem to quantify the metabolic risk factors of cardiovascular disease in severe obese subjects, but AFI is probably useful in obese populations with BMI < 45 kg/m², even though not as strong as waist girth.