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 18 years. 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 12 years, 12 and 13 years, 13 and 14 years, and 15 and 16 years were different from each other (p < 0.05). For girls the only mean vectors with significant differences were 11 and 12 years (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.

UCP1 and UCP3 Expression Is Associated with Lipid and Carbohydrate Oxidation and Body Composition.

BACKGROUND/OBJECTIVE: Uncoupling proteins (UCPs) are located in the inner membrane of mitochondria. These proteins participate in thermogenesis and energy expenditure. This study aimed to evaluate how UCP1 and UCP3 expression influences substrate oxidation and elicits possible changes in body composition in patients submitted to bariatric surgery. SUBJECTS/METHODS: This is a longitudinal study comprising 13 women with obesity grade III that underwent bariatric surgery and 10 healthy weight individuals (control group). Body composition was assessed by bioelectrical impedance. Carbohydrate and fat oxidation was determined by indirect calorimetry. Subcutaneous adipose tissue was collected for gene expression analysis. QPCR was used to evaluate UCP1 and UCP3 expression. RESULTS: Obese patients and the control group differed significantly in terms of lipid and carbohydrate oxidation. Six months after bariatric surgery, the differences disappeared. Lipid oxidation correlated with the percentage of fat mass in the postoperative period. Multiple linear regression analysis showed that the UCP1 and UCP3 genes contributed to lipid and carbohydrate oxidation. Additionally, UCP3 expression was associated with BMI, percentage of lean body mass, and percentage of mass in the postoperative period. CONCLUSIONS: UCP1 and UCP3 expression is associated with lipid and carbohydrate oxidation in patients submitted to bariatric surgery. In addition, UCP3 participates in body composition modulation six months postoperatively.