Guida Bruna, Pietrobelli Angelo, Trio Rossella, Laccetti Roberta, Falconi Claudio, Perrino Nunzia Ruggiero, Principato Silvestre, Pecoraro Pierluigi
Department Neuroscience/Physiology Nutrition Session, University "Federico II", Napoli, Italy.
Nutr Metab Cardiovasc Dis. 2008 Feb;18(2):133-41. doi: 10.1016/j.numecd.2006.08.008. Epub 2007 Feb 16.
To describe bioelectrical impedance vector distribution in relation to BMI (body mass index; body weight/stature(2)) in a population of healthy children in order to detect possible changes in body composition status.
Observational study involving 464 healthy 8-year-old children. The subjects were divided into three groups based on their BMI: 218 normal weight (NW) children with BMI<18.4 for male and BMI<18.3 for female; 135 overweight (OW) children with BMI 18.4 to <21.6 for male and with BMI 18.3 to <21.6 for female; 111 obese (OB) children with BMI>/=21.6. Skinfold thickness was measured at the triceps using a Holtain caliper. Bioelectrical impedance analysis (BIA) measurements were performed. Total body water (TBW), fat-mass (FM), fat-free mass (FFM), body cell mass (BCM) and extra-cellular water (ECW) were estimated using conventional BIA regression equations. The resistance-reactance graph (RXc graph) method was used for vector BIA using as reference population the set of 353 children with BMI 14.0-21.5kg/m(2).
Mean vector displacement followed a definite pattern, with progressive vector shortening in groups with increasing BMI class, and along a fixed phase angle. This pattern indicates an increase in TBW due to an increase in soft tissue mass with an average, normal hydration. In NW children, vectors out of the right and upper half of the 75% tolerance ellipse indicating leanness, and vectors falling out of the right and lower half of the tolerance ellipse indicating undernutrition, show a significantly reduced value of BCM but no significant differences in FM or triceps skinfold thickness (TST), respectively, compared to vectors falling within the 75% tolerance ellipse.
Although BMI is a reliable measure to grade overweight, it cannot differentiate whether weight change is due to variation of FM, FFM or water. In our study a different impedance vector pattern has been associated with normal weight to obesity, and we have established the trajectory followed by the impedance vector of standardized age, healthy children grouped by BMI. This BIVA may be useful for clinical purposes due to ability to detect changes in hydration or body composition in children.
描述健康儿童群体中生物电阻抗矢量分布与BMI（体重指数；体重/身高²）的关系，以检测身体成分状态的可能变化。
对464名8岁健康儿童进行观察性研究。根据BMI将受试者分为三组：218名正常体重（NW）儿童，男性BMI<18.4，女性BMI<18.3；135名超重（OW）儿童，男性BMI为18.4至<21.6，女性BMI为18.3至<21.6；111名肥胖（OB）儿童，BMI≥21.6。使用霍尔坦卡尺测量肱三头肌皮褶厚度。进行生物电阻抗分析（BIA）测量。使用传统的BIA回归方程估算总体水（TBW）、脂肪量（FM）、去脂体重（FFM）、身体细胞质量（BCM）和细胞外水（ECW）。电阻抗图（RXc图）方法用于矢量BIA分析，并将BMI为14.0 - 21.5kg/m²的353名儿童作为参考人群。
平均矢量位移遵循一定模式，随着BMI等级增加，各组矢量逐渐缩短，且沿固定相角变化。这种模式表明，由于软组织质量增加且水化正常，TBW增加。在NW儿童中，位于75%耐受椭圆右半部分和上半部分之外的矢量表示消瘦，位于耐受椭圆右半部分和下半部分之外的矢量表示营养不良，与位于75%耐受椭圆内的矢量相比，BCM值显著降低，但FM或肱三头肌皮褶厚度（TST）无显著差异。
尽管BMI是评估超重的可靠指标，但它无法区分体重变化是由于FM、FFM还是水的变化。在我们的研究中，不同的阻抗矢量模式与正常体重至肥胖相关，并且我们确定了按BMI分组的标准化年龄健康儿童阻抗矢量的轨迹。由于能够检测儿童水化或身体成分的变化，这种生物电阻抗矢量分析（BIVA）可能对临床有帮助。
