Predictors of the metabolic syndrome and correlation with computed axial tomography

Abstract

Objective

We investigated which anthropometric variables or imaging techniques, dual-energy x-ray absorptiometric densitometry (DXA) or bioelectric impedance analysis (BIA), are the most important determinants of the metabolic syndrome. We also evaluated the correlation between anthropometric parameters and DXA and computed axial tomography (CAT) in predicting visceral fat.

Methods

In a series of 399 overweight or obese patients (29.8% male and 70.2% female), anthropometric variables and imaging techniques (DXA or BIA) were measured and correlated with each component of the metabolic syndrome (diagnosed according to the criteria of the Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults of the National Cholesterol Education Program [Adult Treatment Panel III], with the exception of waist circumference). In a subpopulation of 109 patients, CAT was used to assess visceral fat and its correlation with the anthropometric variables and DXA.

Results

Applying receiver operating characteristic curves, the waist/height ratio was the best determinant of the metabolic syndrome (0.758, 95% confidence interval 0.634–0.882). The intra-abdominal diameter determined by DXA (r = 0.657, P < 0.001) and the waist/hip ratio (r = 0.603, P < 0.001) had the best correlation with visceral fat as measured by CAT.

Conclusion

The prediction of visceral fat in overweight and obese patients, as assessed by anthropometric tests and DXA, offers a good alternative to CAT, without significant differences between them.

Introduction

Recent studies have reported that intra-abdominal fat plays an important role in the metabolic syndrome because it is predictive of insulin sensitivity and is closely related to the development of type 2 diabetes, coronary disease, and cardiovascular mortality, independent of total body fat [1], [2], [3], [4].

Janssen et al. [5] reported that an increase in visceral fat in 341 Caucasians, assessed by magnetic resonance imaging (MRI), is more closely correlated to waist circumference than to body mass index (BMI). Likewise and based on data from the Third National Health and Nutrition Examination Survey involving 9019 Caucasians, Zhu et al. [6] reported that waist circumference is linked more closely to cardiovascular disease factors than is BMI. However, the superiority of waist circumference as a clinical tool should be questioned, as reported by the European Group for the Study of Insulin Resistance [7], which showed that the magnitude of the correlation between insulin resistance and obesity does not increase when the waist/hip ratio is replaced by BMI as a marker of obesity.

Although abdominal fat is associated closely with cardiovascular risk factors and metabolic status, anthropometric parameters cannot measure abdominal fat directly [8], [9], [10], [11]. In contrast, dual-energy x-ray absorptiometric densitometry (DXA) and bioelectric impedance analysis (BIA) are potentially more precise for measuring regional adiposity than are anthropometric parameters. Moreover, DXA and BIA are more practical and less costly but less precise than MRI or computed axial tomography (CAT).

The present study investigated which anthropometric parameters or imaging techniques are the best determinants of the metabolic syndrome and whether DXA alone or combined with anthropometry is a good alternative to CAT in predicting visceral fat.