I found this in another forum. Since we have discussed it before I
thought it might interest some people.

Ray

J Clin Endocrinol Metab. 2003 Dec;88(12):6015-9. Related Articles,
Links
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Water-induced thermogenesis.

Boschmann M, Steiniger J, Hille U, Tank J, Adams F, Sharma AM, Klaus
S, Luft FC, Jordan J.

Franz-Volhard Clinical Research Center and Helios-Klinikum-Berlin,
Medical Faculty of the Charite, Humboldt-University, D-13125 Berlin,
Germany.

Drinking lots of water is commonly espoused in weight loss regimens
and is regarded as healthy; however, few systematic studies address
this notion. In 14 healthy, normal-weight subjects (seven men and
seven women), we assessed the effect of drinking 500 ml of water on
energy expenditure and substrate oxidation rates by using whole-room
indirect calorimetry. The effect of water drinking on adipose tissue
metabolism was assessed with the microdialysis technique. Drinking 500
ml of water increased metabolic rate by 30%. The increase occurred
within 10 min and reached a maximum after 30-40 min. The total
thermogenic response was about 100 kJ. About 40% of the thermogenic
effect originated from warming the water from 22 to 37 C. In men,
lipids mainly fueled the increase in metabolic rate. In contrast, in
women carbohydrates were mainly used as the energy source. The
increase in energy expenditure with water was diminished with systemic
beta-adrenoreceptor blockade. Thus, drinking 2 liters of water per day
would augment energy expenditure by approximately 400 kJ. Therefore,
the thermogenic effect of water should be considered when estimating
energy expenditure, particularly during weight loss programs.

PMID: 14671205 [PubMed - indexed for MEDLINE]