Dual energy X-ray absorptiometry assessment of fat mass distribution and its association with the insulin resistance syndrome

OBJECTIVE - To determine which dual energy X-ray absorptiometry (DXA)-deriv ed indices of fat mass distribution are the most informative to predict the various parameters of the metabolic syndrome. RESEARCH DESIGN AND METHODS - A total of 87 healthy men, 63 lean (% fat les s than or equal to 26) and 24 obese (% fat >26), underwent DXA scanning to evaluate body composition with respect to the whole body and the trunk, leg , and abdominal regions from L1 to L4 and from L3 to L3. These regions were correlated with insulin sensitivity determined by the euglycemic-hyperinsu linemic clamp, insulin area under the curve after oral glucose tolerance te st (AUC I); triglyceride; total, HDL, and LDL cholesterol; free fatty acids ; and blood pressure. The analyses were performed in all subjects, as well as in lean and obese groups separately RESULTS - Among the various indices of body fat, DXA-determined adiposity i n the abdominal cut at 11-4 level was the most predictive of the metabolic variables, showing significant relationships with glucose infusion rate ([G IR], mg . kg(-1) lean body mass . min(-1)), triglyceride, and cholesterol, independent of total-body mass (r = -0.267, P < 0.05; r = 0.316, P < 0.005, and r = 0.319, P < 0.005, respectively). Upon subanalysis, these correlati ons remained significant in lean men, whereas in obese men, only BMI and th e amount of leg fat (negative relationship) showed significant correlations with triglyceride and cholesterol (r = 0.438, P < 0.05; r = 0.458, P < 0.0 5; r = -0.439, P < 0.05; and r = -0.414, P < 0.05, respectively). The resul ts of a multiple regression analysis revealed that 47% of the variance in G IR among all study subjects was predicted by AUC I, fat L1-4, diastolic blo od pressure (dBP), HDL, and triglyceride as independent variables. In the l ean group, fat L1-4 alone accounted for 33% of the variance of GIR, whereas in obese men, AUC I and dBP explained 68% of the variance in GIR. CONCLUSIONS - The DXA technique applied for the evaluation of fat distribut ion can provide useful information regarding various aspects of the insulin resistance syndrome in healthy subjects. DXA can be a valid, accurate, rel atively inexpensive, and safer alternative compared with other methods to i nvestigate the role of abdominal body fat distribution on cardiovascular ri sk factors.