Can eating ice make you gain weight? --- Marie, Van Buren, Ark.
Marshall Brain answered:
Let's say that one day you drank half a gallon (roughly 2 liters) of water. That's roughly 4 pounds of water. As soon as you drank it, you would gain four pounds. But over the course of a few hours, you would pee, exhale and sweat away all that water and your weight would return to its former level. You would not "gain weight" from drinking the water, because the water contains no calories.
Now let's say you eat four pounds of ice. It's the same thing as drinking four pounds of water - you will gain weight, but only for a few hours. Then your body will return to its prior weight.
There is something else about ice. Your body is going to use heat to melt the ice. In the summer there is plenty of heat to spare (that's why you are sweating in the summer). But in the winter, your body will actually have to burn calories to warm that ice up (in the same way that your body has to burn calories to stay warm when you are outside on a frosty day). It takes 80 Calories per liter of ice to melt it, and another 66 Calories to raise the temperature of the water up to body temperature. So you will actually lose weight by eating ice.
See also: Does drinking ice water burn calories?