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ACCURACY OF TETRAPOLAR BIOELECTRICAL IMPEDANCE ANALYZER TO DETECT HYDRATION STATUS DURING A WEIGHT LOSS PERIOD

Abstract

Venkataraghavan Ramamoorthy1, Shayne Allan1, Kevin J. Finn, FACSM1 1University of Central Missouri, Warrensburg, Missouri

Bioelectrical impedance analyzer (BIA) estimates various body composition measures, but its role in measuring hydration status is not clinically widespread. Comparing plasma osmolality at the time of the BIA estimations, could help us understand whether BIA detects changes in hydration levels especially during weight loss. PURPOSE: Therefore, the purpose of this study was to evaluate the accuracy of the BIA using bi-monthly measurements of body hydration status and body composition over a two-month period. METHODS: Fifteen healthy females (Mean age = 46.5+9.5 years) consented to participant in the study over an eight-week period, during which they also participated in a weight loss program. Body mass (BM), fat mass (FM), skeletal muscle mass (SMM), intracellular (ICW) and extracellular water (ECW) were measured by InBody 570 Bioelectrical Impedance Analyzer. Subsequently, plasma was collected through venipuncture and blood processing and injected into an Advanced Instruments 3320 Osmometer. Repeated measures analysis of variance (ANOVA) were used to compare the variables. RESULTS: Six females showed a reduction in body mass (group-1) while the remaining seven women served as the comparison group (group-2). Table 1 lists the mean (SD) for ICW, ECW, ECW/TBW, and plasma osmolality. No significant interactions or simple effects were evident in ICW or ECW. No interaction for plasma osmolality was evident however simple effects for plasma osmolality was significant (F=7.5, p=0.001) with an increase in osmolality between week 1 and week 2 for both groups. CONCLUSION: Plasma osmolality increased in both groups at the onset of the weight loss program although not reflective in the measures of ECW or ECW/TBW suggesting a lack of sensitivity of the BIA in detecting this change in hydration status. Further research is needed to develop a better understanding of the accuracy of BIA estimates in determining body hydration status during weight loss.

ACKNOWLEDGEMENTS: Funded by the UCM Professional Development Assistance Grant.

Additional Files
Ramamoorthy Table 1.docx (197 kB)
Table 1

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