from: http://walking.about.com/cs/howtolos...ater011204.htm
Drinking More Water Burns a Few More Calories
From Wendy Bumgardner,Your Guide to Walking.
But Don't Overdo It
Does drinking more water really help dieting? A small study says it may help you burn a few more calories each day. How many? About 50 calories per liter or quart of water. About 25 calories per water bottle-full of water. Mind you, that's only 5 M&Ms - plain, not peanut.
Why Drink More When Dieting?
Drinking a big glass of water whenever you feel hungry and before a meal or snack fills the stomach briefly and makes you feel fuller and stop eating sooner.
Breaking down body fat and body muscle during weight loss produces wastes that must be eliminated through the kidneys. Drinking enough water is important to keep the kidneys functioning to remove these wastes.
Popular high-protein diets produce more waste products from digestion, let alone from breaking down stored fat. Kidney function is even more important when on a high-protein diet.
Drinking more water does not "flush fat."
If the dieter is drinking plain water, he/she is less likely to be drinking something with calories in it.
Drinking Water Briefly Increases Metabolism
Drinking 500 mL of water (a half-liter or about a pint) increased the study participants' metabolism briefly - for about a half hour. In that time they burned an extra 25 calories. That's about a quarter of a piece of sliced bread, or 5 M&Ms. The researchers theorized that most of the effect comes from warming the water in the stomach. In the male participants the calories came mostly from stored fat, in the women it came from stored carbohydrates. The paper was published in the Journal of Clinical Endocrinology and Metabolism, December, 2003. It was conducted by researchers in Berlin. Eight Glasses of Water a Day?
The study provides some support for the general recommendation to drink eight glasses of water a day while dieting. For most people that would add a liter or two to their regular water intake. The extra calorie-burn would be about 100 calories a day if drinking 2 liters (2 quarts or 4 water-bottles full) more than usual.
Dangers of Too Much Water
Don't start drinking an extra gallon of water a day - that can kill you, especially if you are fasting or eating very little. Water taken in must be in balance with body salt - electrolytes. The body needs to maintain salt balance or risk hyponatremia with heart attack and even death. Drinking too much water dilutes the salt in your blood and tissues - and can kill you. Healthy athletes have died from drinking too much plain water and not replacing salt. Dieters should not plunge into drinking gallons of water a day in hopes of burning a few more calories. Drink an extra few glasses, yes. But a gallon is too much.
Drinking and Walking
Exercise such as walking causes the metabolism to rise and body water to be lost through increased respiration and sweat. Walkers should drink a large glass of water an hour before walking, then drink about a cup of water every mile. When you finish walking, drink a glass of water. Guidelines for the marathon and half-marathon now say to "drink when thirsty" rather than pushing water, in order to prevent hyponatremia - drinking too much with replacing electrolytes.
I've been drinking ice water since reading this. Hey, every little bit helps--especially over time the calories will add up.
(a.k.a - "Purple Sunshine" ) 
