A study presented at the European Congress on Obesity (ECO) in Liverpool has found that drinking distilled water has virtually no effect on resting energy expenditure, while mineral water has only a very small effect. The research is by Nathalie Charrière and Professor Abdul Dulloo at the University of Fribourg, Switzerland, and colleagues.
Drinking large amounts of water is often recommended for weight control -a notion which is supported by reports (see references 1-4 below) that drinking 500 ml of water increases resting energy expenditure (REE) by up to 30% during the 30-90min post-ingestion. “These findings are, however, inconsistent with other human studies (see reference 5) reporting no significant thermogenic response to similar, or even greater water load,” say Charrière and Dulloo. “One explanation for these conflicting results may reside in the fact that studies reporting ‘water-induced thermogenesis’ utilise tap water or bottled mineral water, both of which contain ingredients (minerals, salts, pollutants, etc) which may be contributing to the thermogenic effects of water.”
Charrière and colleagues did a study in a total of 16 young men (20-30 years old), in whom REE was measured by ventilated hood indirect calorimetry before and for 2 h after drinking water (water temperature was kept at 21°C). The researchers found that drinking 500 ml of purified (distilled) water did not result in a significant increase in REE in 16 men (a mean increase of just 1.3% in REE that was not statistically significant). By contrast, drinking 500 ml of bottled mineral water (rich in calcium, magnesium, sodium, sulphate, bicarbonate) resulted in a statistically significant but still modest increase of 5.8% REE.
Furthermore, no significant differences were found in REE after drinking 500 ml of distilled water together with the ingestion of capsules of sodium bicarbonate in amounts equivalent to (or double) that present in the bottled mineral water compared to ingestion of water and placebo capsules.
“Our results suggest that drinking 500 ml of purified water has little or no effect on REE,” conclude Charrière and Dulloo. “Whether the presence of minerals or salts (other than bicarbonates) and/or sensorial effects may explain differential thermogenic responses to water remains to be investigated.”
Professor Dulloo’s laboratory is planning further experiments on two fronts: first, to explain the large discrepancy in reported thermogenic effects of water across the various countries (references 1-5), and second to analyse further the thermogenic effect of water as part of our research interests in the search for compounds that stimulates thermogenesis and fat oxidation for weight control (reference 6).
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