RESUMO
BACKGROUND: Bioelectrical impedance analysis (BIA) can be used to estimate body composition. To achieve the best results, the manufacturer's guidelines advise that individuals should restrict intake of food or caffeine, avoid vigorous exercise for 4 hours, and drink 2–4 glasses of water 2 hours before testing. We evaluated the appropriacy of drinking 2–4 glasses of water 2 hours before the BIA, as the validity of this indication has not been specifically demonstrated, by comparing intracellular water (ICW), extracellular water (ECW), total body water (TBW) in the fasting state, and after 1 and 2 hours of ingesting 500 mL of water.METHODS: Twenty-nine healthy adult men (n=10) and women (n=19) were recruited for the study. In the fasting state, the InBody 720 analyzer was used as multi-frequency (MF)-BIA and the output was recorded to determine the exact weight. Subsequently, Medinex BIA 450 analyzer was used as single-frequency (SF)-BIA, and the output was recorded. After drinking 500 mL of water 1 or 2 hours before assessment, the BIA tests were repeated as indicated above, and the ICW, ECW, TBW were compared by repeated measures ANOVA.RESULTS: SF-BIA measurements showed that compared to fasting state, the ICW decreased by approximately 0.56 L after 1 hour of drinking (P=0.001). The ECW was increased by about 0.62 L, 1 hour after drinking water compared to the fasting state (P=0.002). There were no significant differences between the results of BIA testing at 1 and 2 hours of fluid intake. The MF-BIA measurements indicated that testing after fasting, or 1 or 2 hours after fluid intake, did not result in significantly different ICW and ECW values. TBW showed no significant differences in the fasting state, or after 1 or 2 hours of fluid intake for both SF and MF.CONCLUSION: Several studies have shown that bioelectrical impedance should be measured in the fasting state. But not the food intake, drinking 500 mL of water may be permitted when measuring MF-BIA. However, for SF-BIA measurements, fluid intake resulted in an increase in the ECW level and a decrease in ICW.
Assuntos
Adulto , Feminino , Humanos , Masculino , Composição Corporal , Água Corporal , Cafeína , Ingestão de Líquidos , Água Potável , Ingestão de Alimentos , Impedância Elétrica , Óculos , Jejum , Vidro , ÁguaRESUMO
The purpose of this study was to compare estimates of human body composition determined from single-frequency bioelectrical impedance methods (S-BIM) and multi-frequency bioelectrical impedance methods (M-BIM) . The human body composition was assessed by dual energy X-ray absorptiometry (DEXA), 5 brands of S-BIM, and 2 brands of M-BIM. Forty-five women, aged 26-58 years, served as subjects. The S-BIM and M-BIM fat-free mass (FFM) estimates were highly correlated with the FFM measured by DEXA (r=0.82-0.93) . The standard errors of estimate (SEE) for FFM were approximately 2 kg. With the exception of the MLT-100 (which slightly underestimated FFM), all brands of BIM slightly overestimated FFM. The absolute mean differences between FFMDEXA and each of the 7 BIM estimates ranged from -3.02 kg to 3.46 kg. Although the 7 brands of BIM provided slightly different estimates, the results of this study suggest that 5-BIM and M-BIM are relatively valid in human body composition.
RESUMO
The purpose of this study was to compare estimates of human body composition determined from single-frequency bioelectrical impedance methods (S-BIM) and multi-frequency bioelectrical impedance methods (M-BIM) . The human body composition was assessed by dual energy X-ray absorptiometry (DEXA), 5 brands of S-BIM, and 2 brands of M-BIM. Forty-five women, aged 26-58 years, served as subjects. The S-BIM and M-BIM fat-free mass (FFM) estimates were highly correlated with the FFM measured by DEXA (r=0.82-0.93) . The standard errors of estimate (SEE) for FFM were approximately 2 kg. With the exception of the MLT-100 (which slightly underestimated FFM), all brands of BIM slightly overestimated FFM. The absolute mean differences between FFMDEXA and each of the 7 BIM estimates ranged from -3.02 kg to 3.46 kg. Although the 7 brands of BIM provided slightly different estimates, the results of this study suggest that 5-BIM and M-BIM are relatively valid in human body composition.