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Methods for Estimating Body Fat Distribution as a Risk Factor for Cardiovascular Disease: Agreement of Waist-to-Hip with Truncal Reactance-to-Resistance Ratios

Carlo De Palo, R. Gatti^, E. Cappellin^, E.F. De Palo^ and P. Spinella*

Internal Medicine,*Clinical Nutrition and ^Clinical Biochemistry Chairs
University of Padova
Padova, Italy

Abstract
Introduction
Objectives
Material and Methods
Results
Discussion
Conclusions
References

Abstract
Background: The distribution of excess adipose tissue profoundly affects its role as a risk factor for cardiovascular disease (CVD). Evidence has accumulated indicating that intra-abdominal fat distribution contributes to CVD. A simple method for the assessment of fat distribution is Waist-Hip circumference (cm) Ratio (WHR).
Objective: Evaluation of the agreement of WHR and segmental (i.e., arm, trunk and leg) Bioelectric Impedance Analysis.
Subjects: Initially we found that in 592 subjects the reactance-to-resistance ratio (Xc/R) was significantly positively correlated with the Body Mass Index (BMI: weight (kg)/height (m2) (p=0.037). The (Xc/R)/BMI was significantly correlated with the insulin resistance markers and with the basal diastolic pressure increase, an early alteration of CVD (r = 0.38; p = 0.0001). We measured, as proposed by Organ LW et al.(J App Physiol 77(1),98,1994), "virtual" Truncal reactance to Truncal resistance ratio (vTXc/vTR) in 28 obese females (BMI = 36.1 ± SD 8.0) and in 26 control subjects [14 female/12 male] (BMI = 23.3 ± 3.2).
Results: The WHRs were similar between the control groups, but the vTXc/vTR was significantly higher in the control than in the obese group (p < 0.03).In a multiple linear regression analysis, with the vTXc/vTR as dependent variable, neither BMI and age, but only WHR contributed to the variance of vTXc/vTR (R2 = 0.434; p = 0.0105).
Conclusions: These results show a clear association between vTXc/vTR ratio and WHR in estimating central fat distribution. Therefore, the vTXc/vTR, as an early marker of central obesity together with its possible association with diastolic disfunction could be proposed as a prognostic marker of CVD.

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Introduction:

The distribution of excess adipose tissue profoundly affects its role as a risk factor for cardiovascular disease (CVD). Recently, evidence has accumulated indicating that intra-abdominal visceral fat accumulation contributes to CVD. A common and simple method for the assessment of body fat distribution is Waist circumference (cm)/Hip circumference (cm) Ratio (WHR). Cefalu WT et al. (1) found that WHR is more strongly related to visceral than subcutaneous fat mass, quantified using a validated magnetic resonance imaging scanning technique.

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Objectives:

In this current study,the objective is the evaluation of the agreement of abdominal body fat distribution estimated by WHR measurement and segmental Bioelectric Impedance Analysis (BIA) method (i.e., arm,trunk and leg), using adhesive electrodes placed, as proposed by Organ LW et al. (2) (see scheme). The BIA method is based on the concept that an electrical current is conducted by the electrolytes dissolved in body fluids, and the Resistance (R) and reactance (Xc) measured are inversely proportional to the amount of fluid volume present and directly related to cellular mass, respectively.

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Material and Methods:

Design
Cross-sectional data obtained from the baseline study population. Informed consent was obtained from all partecipants.

Subjects
In a preliminary study we found in 592 subjects no resistance-to-reactance, but only that reactance-to-resistance ratio (Xc/R) was significantly positively correlated with the Body Mass Index [BMI: weight (Kg)/height (m2)] (p = 0.037). In addition, the Xc/R, stratified for BMI, was significantly correlated with the fasting C-peptide levels, an index of pancreatic insulin production and, in turn, hyperinsulinemia with, possibly, insulin resistance (R2 = 0.82; p < 0.00001). Furthermore the Xc/R, divided for BMI, was significantly negatively correlated with the resting diastolic pressure, an early alteration of cardiac function (Fig 1:r = 0.38; p = 0.0001). In the present study we measured the effects of an application to the skin of an electrical current of 50 kHz and 0.8 mA, using adhesive electrodes placed, as proposed by Organ, during BIA, on "virtual" Truncal reactance to Truncal resistance ratio (vTXc/vTR) in 28 Obese Female (OF) subjects (BMI= 36.1±sd 8.0 kg/m2) and in 26 Control (C) subjects [14 F / 12 Male (M)] (BMI=23.3±3.2). "Virtual" bioelectric impedances were obtained in fasted subjects and at the same time anthropometric measurements included the WHR. Waist and hip circumferences were measured midway between the lower rib margin and the superior iliac spine and at the widest point over the greater trochanters, respectively.

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Results:

The WHRs were similar between the control groups, but the vTXc/vTR was significantly higher in the control than in the obese group (Tab 1).

Table 1: Demographic,body composition, and indirect fat distribution index

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° Significantly different total control and obese female subjects (Total C vs OF: p < 0.03).

In a multiple linear regression analysis, with vTXc/vTR as dependent variable, neither BMI and age, but only WHR contributed to the variance of vTXc/vTR (R2 = 0.434; p = 0.0105) (Fig 2, Fig 3).

 

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Discussion:

The results of our study showed a clear association between vTXc/vTR ratio and WHR in estimating the differences in segmental body composition and, in turn, in abdominal fat. This abdominal-related measurement of vTXc/vTR might support the concept that increased visceral adipose tissue mass with a high density of adipocytes could be related to truncal cellularity. Perhaps, the subjects with higher abdominal fat mass or, in turn, visceral fat mass are prone to exhibit lower vTXc/vTR ratios.

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Conclusions:

Therefore, the vTXc/vTR ratio measurement might be used to estimate the abdominal and/or visceral fat mass in humans. Employment of this early marker of central obesity together with its, possibly, association with diastolic disfunction that may precede the overt clinical expression of several CVD, in the future may lead to the elaboration of more adequate preventive measures.

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References

1. Cefalu WT, et al.: Metabolism, vol 44:7,954,1995.
2. Organ LW, et al.: App Physiol 77 (1),98,1994.

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Questions, contributions and commentaries to the Authors: send an e-mail message (up to 15 lines, without attachments) to epi-pcvc@pcvc.sminter.com.ar , written either in English, Spanish, or Portuguese.

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© CETIFAC
Bioengineering
UNER

Update
Dic/23/1999


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