Is bioelectrical impedance vector analysis a good indicator of nutritional status in children and adolescents?

OBJECTIVE: The study objective is to propose bioelectrical impedance vector analysis (BIVA) ellipses for the population and investigate its use to assess nutritional status through the BMI/age ratio and the cardiovascular risk through waist circumference (WC). DESIGN: Age, weight, height and WC were recorded, along with the values of resistance (R), reactance (Xc) and phase angle (PA) by impedance. Student's t test and ANOVA were applied to ascertain the significance between means and a specific programme was applied to investigate the significance between ellipses. SETTING: Fortaleza, Brazil. PARTICIPANTS: A total of 467 students from public schools participated in the study: 120 children and 347 adolescents were evaluated, with respective means of age, weight and height of 8·2 years, 27·6 kg and 1·29 m and 12·7 years, 48·6 kg and 1·53 m, respectively. RESULTS: The mean values of R/H, Xc/H and PA were 569·0 and 424·7 Ohm/m, 59·1 and 50·4 Ohm/m, and 5·9º and 6·8º for children and adolescents, respectively. The mean vectors for R/H and Xc/H show significant differences between for both age ranges and are inversely proportional to the BMI/A. As for WC, individuals without cardiovascular risk had higher R/H and lower Xc/H, but Xc and R in participants without cardiovascular risk were greater than with cardiovascular risk. CONCLUSIONS: It was possible to propose confidence and tolerance BIVA ellipses for children and adolescent's clinical evaluation. The method was also suitable to identify cardiovascular risk ellipses in these age groups, but it was not possible to draw nutritional classifications ellipses by BMI/age data.