title: The influence of oral water load on energy expenditure and sympatho-vagal balance in obese and normal weight women.
abstract: BACKGROUND
  Oral water load may increase the energy expenditure (EE) by stimulation of sympathetic dependent thermogenesis. Thus, drinking of water may be helpful in weight reduction. The aim of the study is to assess the influence of water load on energy expenditure and sympathetic activity in obese and normal weight women.
  
  
  METHODS
  Forty-five women were included. Energy expenditure was measured twice, in the morning and after oral water load, by the indirect calorimetric method. The heart rate variability parameters low frequency (LF), high frequency (HF), LF/HF index, standard deviation of normal RR intervals (SDNN) and root mean square difference among successive RR normal intervals (rMSSD) were used for the indirect assessment of the sympatho-vagal balance.
  
  
  RESULTS
  Resting energy expenditure (REE) was significantly higher in obese than in normal weight women (1529 ±396 kcal/day vs. 1198 ±373 kcal/day; p = 0.02). In both study groups after water load EE increased significantly (by 20% and by 12%, corresponding to 8.6 kcal/h and 5.2 kcal/h respectively), while, LF/HF index increased simultaneously. The increase of energy expenditure (EE) did not exceed the energetic cost of water heating, from room to body temperature - 15 kcal/1000 ml. There was no correlation between changes of energy expenditure (EE) and heart rate variability (HRV) parameters.
  
  
  CONCLUSIONS
  The increase of EE induced by water load is mostly related to the heating of the consumed water to body temperature. The assessment of autonomic balance by means of standard HRV indices had been found insufficient for detection of actually operating mechanisms.
authors: Health Promotion and Obesity Management Unit, Department of Pathophysiology, Medical University of Silesia, Katowice, Poland.
authors: Piotr
authors: P
authors: Kocełak
authors: Agnieszka
authors: A
authors: Zak-Gołąb
authors: Anna
authors: A
authors: Rzemieniuk
authors: Joanna
authors: J
authors: Smętek
authors: Ryszard
authors: R
authors: Sordyl
authors: Agata
authors: A
authors: Tyrka
authors: Maciej
authors: M
authors: Sosnowski
authors: Barbara
authors: B
authors: Zahorska-Markiewicz
authors: Jerzy
authors: J
authors: Chudek
authors: Magdalena
authors: M
authors: Olszanecka-Glinianowicz
keywords: energy expenditure; obesity; oral water load; sympatho-vagal balance