title: The effect of acute fluid consumption on measures of impedance and percent body fat estimated using segmental bioelectrical impedance analysis.
abstract: OBJECTIVE
  To determine the effect of acute fluid consumption on measures of impedance and percent body fat (%BF) estimated using segmental bioelectrical impedance analysis (SBIA).
  
  
  METHODS
  Seventy-six healthy, recreationally active adults (41 women; 35 men) volunteered to participate in this study (mean+/-s.d.; age, 21.0+/-1.6 years; body mass index, 25.0+/-3.2 kg/m2). Subjects had their body composition assessed on three separate occasions. After a baseline measurement, subjects consumed 591 ml of water (H2O), a carbohydrate/electrolyte drink (CHOE) or received nothing (CON). Subjects were reassessed 20, 40 and 60 min following (POST) the baseline measure in each fluid condition.
  
  
  RESULTS
  Twenty minutes after drinking a H2O or CHOE beverage, %BF (1.1 and 1.2%), impedance (12 and 14 Omega) and body mass increased significantly (P<0.001). During the CON trial, %BF (0.3 and 0.5%) and impedance (7 and 11 Omega) also increased significantly above baseline values at 40 and 60 min POST. However, the normal hourly variability was significantly (P<0.009) less than the observed fluid-induced %BF alterations. The greatest %BF increases were observed in the lightest subjects, who were women. Fluid type had no effect on the magnitude of change POST.
  
  
  CONCLUSIONS
  Twenty minutes after drinking, %BF estimates increased approximately 1.0% due to elevations in impedance and body mass. As such, we recommend adhering to the pretest fluid restriction guideline to avoid fluid-induced alterations in SBIA body composition measures. In addition, use of a consistent testing schedule may minimize normal %BF variation over time.
authors.affiliation: Department of Health Science, Lock Haven University, Lock Haven, PA, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Dixon
authors.forename: L
authors.initials: L
authors.lastname: Ramos
authors.forename: E
authors.initials: E
authors.lastname: Fitzgerald
authors.forename: D
authors.initials: D
authors.lastname: Reppert
authors.forename: J L
authors.initials: JL
authors.lastname: Andreacci
mesh_terms: D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D001823:Body Composition; D001835:Body Weight / Q000502:physiology; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004326:Drinking; D004573:Electrolytes / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D010992:Plethysmography, Impedance; D012737:Sex Factors; D013997:Time Factors; D014867:Water / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D004040:Dietary Carbohydrates; D004573:Electrolytes; D014867:Water