A number of methods exist for the estimation of abdominal obesity, ranging from waist-to-hip ratio to computed tomography (CT). Although dual-energy X-ray absorptiometry (DXA) was originally used to measure bone density and total body composition, recent improvements in software allow it to determine abdominal fat mass. Sixty-five men and women aged 18-72 yr participated in a series of studies to examine the validity and reliability of the DXA to accurately measure abdominal fat. Total body fat and abdominal regional fat were measured by DXA using a Lunar DPX-IQ. Multislice CT scans were performed between L1 and L4 vertebral bodies (region of interest) using a Picker PQ5000 CT scanner, and volumetric analyses were carried out on a Voxel Q workstation. Both abdominal total tissue mass (P = 0.02) and abdominal fat mass (P < 0.0001) in the L1-L4 region of interest were significantly lower as measured by DXA compared with multislice CT. However, Bland-Altman analysis demonstrated good concordance between DXA and CT for abdominal total tissue mass (i.e., limits of agreement = -1.56-2.54 kg) and fat mass (i.e., limits of agreement = -0.40-1.94 kg). DXA also showed excellent reliability among three different operators to determine total, fat, and lean body mass in the L1-L4 region of interest (intraclass correlations, R = 0.94, 0.97, and 0.89, respectively). In conclusion, the DXA L1-L4 region of interest compared with CT proved to be both reliable and accurate method to determine abdominal obesity.

WHR is not associated with S(I) in either men or women. Abdominal adiposity measured by DXA L1-L4 fat mass provides a sex-independent predictor of S(I) in older men and women.

The purpose of this study was to determine whether sodium-resistant hypertensives are more insulin resistant and whether dietary sodium restriction improves insulin sensitivity in older hypertensives. Insulin sensitivity was assessed by a frequently sampled intravenous glucose tolerance test to determine the insulin sensitivity index (SI) after 1 wk each of low- (20 mmol ⋅ l−1 ⋅ day−1) and high- (200 mmol ⋅ l−1 ⋅ day−1) sodium diets in 21 older (63 ± 2 yr) hypertensives. Subjects were grouped on the difference in mean arterial blood pressure (MABP) between diets [sodium sensitive (SS): ≥5-mmHg increase in MABP on the high-sodium diet ( n = 14); sodium resistant (SR): <5-mmHg increase in MABP on the high-sodium diet ( n = 7)]. There was no dietary sodium effect on fasting plasma insulin or SI. An analysis of variance indicated a significant ( P = 0.0002) group effect, with SS individuals having lower fasting plasma insulins on the low- (13 ± 2 vs. 27 ± 3 μU/ml) and high- (12 ± 2 vs. 22 ± 3 μU/ml) sodium diets compared with SR individuals. Similarly, there was a significant ( P= 0.0002) group effect in regard to SI, with SS individuals having significantly higher SI on the low- (3.26 ± 0.60 vs. 0.91 ± 0.31 μU × 10−4 ⋅ min−1 ⋅ ml−1) and high- (3.45 ± 0.51 vs. 1.01 ± 0.30 μU × 10−4 ⋅ min−1 ⋅ ml−1) sodium diets compared with SR individuals. We conclude that SR individuals exhibit a greater degree of insulin resistance than SS individuals and that dietary sodium restriction fails to improve insulin sensitivity regardless of sodium sensitivity status.

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