THE BIA VECTOR IN OBESITY AND DIABETES

Abstract

Although the assessment of body water compartments is of great diagnostic value, appropriate methods are not readily available for routinely clinical application. Bioelectrical impedance analysis (BIA) is a safe, noninvasive, rapid and highly reproducible procedure that is strongly influenced by body water and intra-/extracellular distribution. Four-hundred-fifty-six adults (224 males and 232 females) were enrolled and divided in subgroups on the basis of the presence of obesity and diabetes (type 1 and type 2). The aim of the study was to investigate if different BIA measurements in terms of resistance (R), reactance (Xc) and phase angle (PA) were associated to these conditions. Plotting the average values of R and Xc normalized for height (h), a mean vector was obtained for each group. The vector displacement could be easily recognized on the basis of its length and of the angle described with the abscises axis (PA). When compared to the control groups, the vector resulted to be shorter in presence of obesity. The PA was slightly lower in the diabetic groups when compared to their body size matched non-diabetic groups. Fasting plasma glucose (FPG) was independently correlated to height normalized R (R/h) as in diabetic males (r= 0.40; P< 0.001) and in diabetic females (r= 0.50; P< 0.001). On the basis of BIA principles, these results are in agreement with the possibility that non diabetic obese patients have an increased body-water content but in average they maintain a distribution between intra- (ICW) and extra-cellular (ECW) water compartments similar to that of control subjects. Furthermore, diabetics have an increased ECW size and, as expected, with increasing FPG their body water content proportionally decreases. As a partial confirmation, the BIA vector of 9 diabetics with poor glycemic control was monitored during the course of rehydrating treatment. The BIA vector became progressively shorter but the PA remained unchanged. Therefore, the evolution of the BIA vector was in the sense of a progressive increase of total body water content, equally distributed between ICW and ECW compartments. In conclusion, BIA measurements could be considered as specific body characteristics that expressed in terms of BIA vector may be useful to diagnose and monitoring imbalances of body water compartments.