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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 400 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 400 kilocalories of metabolic energy? For comparison, the stomach can hold about 1 liter.

Any ideas about what formula I need to use ?

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Welcome to stackexchange. You've asked a "do-my-homework" type question. Such questions are not welcome here, unless you make a serious effort to show how what you know about the problem and how you've tried to use that knowledge to solve the problem. – user1504 Dec 5 '12 at 3:02
Why have you assumed this is a homework question? It might be, but it might also be an honest question. I remember asking exactly this question (many) years ago when my Dad told me this "fact". – John Rennie Dec 5 '12 at 10:28

closed as too localized by David Zaslavsky♦ Dec 5 '12 at 3:02

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Q = CM dT, where C is the specific heat of water = 1 Cal/C, dT is the temperature change which is 37 (from 0 to 37) and M is the mass needed. Here Q=400 000 Cal as you stated.

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Please refrain from answering homework questions. We try to discourage these here, because they clutter up the site and don't really help the questioner learn anything. – user1504 Dec 5 '12 at 3:23

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