When you drink cold water, your body must expend metabolic energy in order to maintain normal body temperature (37° C) by warming up the water in your stomach. Could drinking ice water, then, substitute for exercise as a way to "burn calories?" Suppose you expend 390 kilocalories during a brisk hour-long walk. How many liters of ice water (0° C) would you have to drink in order to use up 390 kilocalories of metabolic energy? For comparison, the stomach can hold about 1 liter.