Water has NO calories.
Studies show that our bodies don't register empty calories from liquids like they register calories from food. When you drink 200 calories from a soft drink or fruit-aid, you typically don't adjust the rest of your dietary intake based on those calories. The result is excess calorie consumption, eventually leading to weight gain. Water aids in elimination. Having regular bowel movements keeps dangerous bacteria out of the body and may prevent diseases of the colon such as diverticulosis.