Skeletal Muscle Mass and Extracellular Water/Total Body Water Independently Predict Phase Angle Percentile in Young Men

Abstract Objectives Phase angle, derived from bioelectrical impedance analysis (BIA), is used to describe both cellular and overall health. Many of the variables measured using BIA vary based on the hydration status of the individual. The ratio between extracellular water/total body water is commonly measured in BIA, and can be used as a measure of individual hydration. This pilot study explores the relationship between individual hydration status and phase angle and other BIA measurements. Methods Male college students (n = 57) from Oklahoma State University-Stillwater were recruited through an email messaging campaign. The participants answered an online Qualtrics demographic survey; height (±0.1 cm), blood pressure, and weight were taken. The Seca Medical Body Composition Analyzer mBCA 514 was used to conduct the BIA. Variable mean, standard deviations, and frequencies were calculated using SPSS version 25. Pearson correlation analysis and regression analysis were conducted. Significance was set at <.05. Results Participants characteristics included: age (m = 21.7 ± 1.3 years), 54% BMI <25, 39% blood pressure <120/80, and 63% white/7% Native American. Mean % body fat was 20.28 ± 8.76, and skeletal muscle was 32.223 kg ± 4.432 and visceral fat was 2.01 liters ± 2.11.Phase angle percentile ranged from 1% to 99% (m = 62.0% ± 31.4) and extracellular water/total body water ratio (ECW/TBW) ranged from 35.7 to 41.6 (m = 39.32 ± 1.35). Phase angle percentile was positively correlated with skeletal muscle mass (r = 0.503, P = 0.000) and negatively correlated with ECW/TBW (r = −0.659, P = 0.000), but not with other BIA variables. These two variables significantly predicted phase angle percentile (r2 = 0.817, P = 0.000). The standardized β was −0.762 (P = 0.000) for ECW/TBW and 0.627 (P = 0.000) for skeletal muscle mass. Conclusions The association of ECW/TBW on phase angle percentile suggest further investigation of the impact of water on this indicator of health is warranted. An investigation with a method of modulating ECW/TBW would be a logical next step in understanding this relationship. Funding Sources Funding was provided by the Lew Wentz Foundation, and the Nutritional Sciences Department at Oklahoma State University.