Drinking ice water also has another benefit - it burns Calories!

One calorie is the energy necessary to heat one cc of water one degree celsius. A dietary calorie is actually 1 kcal (one thousand calories) and is enough to raise 1 liter of water one degree celsius. If you drink ice water at 0 C your body has to heat it to 37 C so you are pulling 37 kcal of heat out of your body which has to be made up. Water at room temperature only has to be heated about 8 C. So, if you drink 4 liters of water ice water a day, you would consume 100 additional calories a day compared to drinking ice water. That would correspond to about an additional pound a month.

Now, having said all that, I think there are some occasions when it is not true - namely when your body is already producing so much waste heat that it is having to cool itself through sweating. But I think that as long as you are in a typical room environment (or cooler) and not undergoing physical exertion that this will be the case.

When you think about it, this extra calorie burn would be boosting most peoples' weight loss anywhere from about 5% (for the real lucky ones that are already losing 20#/mo) to 20% (for someone losing 5#/mo) or more.