Did you know that your body weight is approximately 60 percent water? Your body uses water in all its cells, organs, and tissues to help regulate its temperature and maintain other bodily functions. Because your body loses water through breathing, sweating, and digestion, it's important to rehydrate by drinking fluids and eating foods that contain water. The amount of water you need depends on a variety of factors, including the climate you live in, how physically active you are, and whether you're experiencing an illness or have any other health problems.