Current recommendations amongst Western populations include advice to drink more water. However, the health effects of drinking excess water beyond prevention of dehydration are controversial. Studies substituting water for sugar sweetened beverages have shown health benefits in subjects, but other non-sweetened drinks may be just as advantageous. Some evidence also suggests that drinking more water may promote weight loss. For example in a review of previous studies1, researchers assessed the association between daily water consumption and body weight. The authors managed to find 11 original research studies that were eligible for inclusion in their review, and the combined results from these studies showed that increased water consumption was associated with reduced body weight after 3 to 12 months compared to the same programme without inclusion of any water. However, when the authors analysed data from mixed weight populations not trying to lose weight, there was no such association present in the data and the results were far more inconsistent.
Therefore drinking more water may be associated with improved weight loss outcomes in those attempting to lose weight. However, the mechanisms for such an effect is not understood. One possibility is that those that consume more water consume less beverages that may contain sugar or may substitute water as a ‘snack’. This seems the most logical reason for the association, but there may be physiological mechanisms by which water can induce calorie loss. For example one study suggested that the thermogenic effect of water, a phenomenon that water must be heated to body temperature when drunk, suggests that energy loss from drinking may occur. In this study it was suggested that 0.5 L of water increased the metabolic rate by about 30 kcal. It was suggested this energy came from the transfer of heat required to heat the water and therefore created a thermogenic effect in the body. If this is the case drinking chilled water may be a larger thermogenic effect that drinking cool water.
Dr Robert Barrington’s Nutritional Recommendation: It is currently unknown how much water is required for health beyond the recommendation that hydration is maintained. However, while water may increase weight loss in those who are trying, tea and coffee are far more likely to cause weight loss, a contention supported by large volumes of scientific data.
RdB
