After drinking approximately 17 ounces of water, the subjects' metabolic rates -- or the rate at which calories are burned -- increased by 30% for both men and women. The increases occurred within 10 minutes of water consumption and reached a maximum after about 30 to 40 minutes.
The study also showed that the increase in metabolic rate differed in men and women. In men, burning more fat fueled the increase in metabolism, whereas in women, an increased breakdown of carbohydrates caused the increase in metabolism seen.
The researchers estimate that over the course of a year, a person who increases his water consumption by 1.5 liters a day would burn an extra 17,400 calories, for a weight loss of approximately five pounds. They note that up to 40% of the increase in calorie burning is caused by the body's attempt to heat the ingested water. The findings are reported in the December issue of The Journal of Clinical Endocrinology and Metabolism.
