Bioelectrical Impedance of Vectorial Analysis and Phase Angle in Adolescents

Objectives: Bioelectrical impedance can be interpreted by vector analysis using direct measures of the impedance vector; thus, collecting information about resistance (R), reactance (Xc), and phase angle (PA) makes it possible to classify an individual's nutritional status. The aim of this study was to investigate these values and construct bioelectrical references for healthy Brazilian adolescents. Methods: This is a cross-sectional study that included 567 healthy adolescents, aged 10 to 18years. The bioelectrical impedance was performed to collect data for R and Xc. In addition, weight and height were also collected. The PA was calculated, and thereby the tolerance and confidence ellipses were constructed using specific software. Results: For boys the mean vectors of 11 and 12years, 12 and 13years, 13 and 14years, and 15 and 16years were different from each other (p < 0.05). For girls the only mean vectors with significant differences were 11 and 12years (p = 0.0071). The results differ from those in the literature, possibly due to ethnic differences in body composition. Conclusion: The present study provides an important tool for monitoring the nutritional status of adolescents of different ages, without previous knowledge of some anthropometric measures such as body weight.