Guida B, Trio R, Pecoraro P, Gerardi M C, Laccetti R, Nastasi A, Falconi C
Dept. of Neuroscience/Physiology Nutrition Section, Faculty of Medicine, University Federico II, Via S. Pansini, 80131 Napoli, Italy.
Nutr Metab Cardiovasc Dis. 2003 Apr;13(2):72-9. doi: 10.1016/s0939-4753(03)80021-2.
To compare the body fluid status assessments provided by conventional bioelectrical impedance analysis (BIA) and vector BIA in moderate and severe obesity.
We studied 516 normotensive Caucasian women (mean age: 48 +/- 9.2 years), who were age-matched and divided into four groups on the basis of their body mass index (BMI): 99 normal weight women with a BMI of 19-25 Kg/m2; 228 preobese overweight women with a BMI of 25-30 Kg/m2; 132 women with class I-II obesity (BMI: 30-35 Kg/m2), and 57 women with class III obesity (BMI: 40-64 Kg/m2). Single-frequency (50 kHz) tetrapolar (hand-foot) bioelectrical impedance measurements were made, and total body water (TBW) and extracellular water (ECW) were estimated using conventional BIA regression equations. The RXc graph method was used for vector BIA, with the set of 327 women with a BMI of 19-30 Kg/m2 being adopted as the reference population. Mean vector displacement followed a definite pattern, with progressive vector shortening as the BMI increased, and along a fixed phase angle. This pattern indicates more TBW due to a greater soft tissue mass with average normal hydration. Short and downsloping vectors indicating fluid overload were more frequent in the group with class III obesity than in the group with class I obesity (19 vs 5%). The absolute values of TBW and ECW were significantly higher in the obese and overweight subjects than in those with normal weight subjects. TBW as a percentage of body weight was significantly lower in the obese subjects.
BMI influenced the impedance vector distribution pattern, which proved to be consistent up to a BMI of 64 Kg/m2. Obese women with an altered body composition can be identified and monitored using vector BIA.
比较传统生物电阻抗分析（BIA）和矢量BIA对中度和重度肥胖患者体液状态的评估。
我们研究了516名血压正常的白种女性（平均年龄：48±9.2岁），她们年龄匹配，并根据体重指数（BMI）分为四组：99名BMI为19 - 25 Kg/m²的正常体重女性；228名BMI为25 - 30 Kg/m²的肥胖前期超重女性；132名I - II级肥胖女性（BMI：30 - 35 Kg/m²），以及57名III级肥胖女性（BMI：40 - 64 Kg/m²）。进行了单频（50 kHz）四极（手足）生物电阻抗测量，并使用传统BIA回归方程估算总体水（TBW）和细胞外水（ECW）。矢量BIA采用RXc图法，以327名BMI为19 - 30 Kg/m²的女性作为参考人群。平均矢量位移遵循一定模式，随着BMI增加，矢量逐渐缩短，并沿着固定的相位角。这种模式表明由于软组织质量增加且平均水合正常，TBW更多。III级肥胖组中指示液体过载的短且向下倾斜的矢量比I级肥胖组更常见（19%对5%）。肥胖和超重受试者的TBW和ECW绝对值显著高于正常体重受试者。肥胖受试者中TBW占体重的百分比显著较低。
BMI影响阻抗矢量分布模式，在BMI高达64 Kg/m²时该模式保持一致。使用矢量BIA可以识别和监测身体成分改变的肥胖女性。
