Consuming a low-calorie amount of routine food and drink does not affect bioimpedance body fat percentage in healthy individuals.

OBJECTIVES: Bioimpedance analysis is a simple, safe, and relatively inexpensive method to assess body composition. The bioimpedance guidelines recommend that the test be performed after fasting and avoiding the consumption of liquids. Studies have verified the effects of consuming liquids and food on bioimpedance; however, these studies used preestablished meals and hydration. The aim of the present study is to identify whether ad libitum food and liquid intake interfere with body composition parameters estimated via bioimpedance. METHODS: The evaluations were carried out over 2 d. On the first d, the hydration protocol was applied and on the second d, the food protocol. In both cases, bioimpedance was performed after an 8-h overnight fast. The test was repeated 30 min after the intake of liquids or food depending on the protocol. The reproducibility between the pre- and posttest evaluations was assessed using the Bland-Altman method. We considered deviations of up to 5% in the limits of agreement to be clinically acceptable. RESULTS: In the hydration protocol, the mean difference in fat percentage (FP) was -0.50 (P = 0.05), the lower limit of agreement was -3.60%, and the upper limit of agreement was 2.61%. In the food protocol, the mean difference in FP was 0.002 (P = 0.99), the lower limit of agreement was -3.20%, and the upper limit of agreement was 3.20%. CONCLUSIONS: Our study shows that ad libitum food and liquid intake do not cause a change above clinically acceptable levels in the FP estimated by bioimpedance.

Can skinfold thickness equations be substituted for bioimpedance analysis in children?

OBJECTIVE: The aim of the present study was to evaluate the agreement between the most used skinfold thickness equations with multi-frequency bioimpedance analysis in the prediction of body fat levels in children. METHOD: A cross-sectional study of healthy Brazilian community-dwelling individuals. The anthropometric assessment included height, body mass, arm circumference, and waist circumference. The percentage of body fat was obtained by measuring skinfold thickness equations and using bioimpedance analysis, and skinfold thickness was measured using a scientific skinfold caliper. Bland-Altman plot analysis was used to verify the agreement between the methods. RESULTS: There were 439 children and adolescents evaluated, with a mean age of 11.6±3.7 years. The mean body fat by bioimpedance analysis was 22.8%±10.4%, compared to 22.4%±8.8% by Slaughter (1), 20.4%±9.2% by Slaughter (2), 19.6%±4.4% by Goran, and 24.7%±10.0% by Huang equations. Bland-Altman plot analysis revealed limits of agreement greater than 8% between the bioimpedance analysis approach and equations, exceeding the clinically acceptable limit predefined a priori. None of the equations had good agreement with bioimpedance analysis. CONCLUSION: It was concluded that skinfold thickness and bioimpedance analysis should not be used interchangeably in children and adolescents.

Association between phase angle from bioelectrical impedance analysis and level of physical activity: Systematic review and meta-analysis.

OBJECTIVE: To evaluate the relationship between physical activity and phase angle. DESIGN: Systematic Review and Meta-analysis. DATA SOURCES: Electronic searches of MEDLINE (via PUBMED), EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), SciELO, LILACS, SPORTDiscus, Scopus, and Web of Science from inception to December 10th, 2017. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: The PICOS strategy was defined, in which "P" corresponded to participants of any age, sex or ethnicity, "I" indicated any type of physical activity program, "C" denoted lack of exercise or irregular physical activity, "O" corresponded to the phase angle obtained by bio-impedance, and "S" indicated longitudinal or cross-sectional studies. RESULTS: In cross-sectional studies the phase angle was higher among the active individuals (MD = 0.70; 95% CI: 0.48, 0.92, P < 0.001), with low heterogeneity (I2 = 0%; P = 0.619). In longitudinal studies, the mean of the difference of phase angles from the baseline was significantly higher for the active group than the control group (MD = 0.30; 95% CI: 0.11, 0.49, P = 0.001), with low heterogeneity (I2 = 13%, P = 0.331). No evidence of publication bias was found and the overall risk of bias was moderate to high. SUMMARY/CONCLUSION: The positive association of physical activity with phase angle reinforces the importance of routinely including exercise in health care. We also identified the need for further studies to define with different types, intensities and frequencies of exercises should be conducted in order to find the best dose-effect relationship.