Did you know that your weight is about 60 percent water? Your body uses water in all cells, organs and tissues to help regulate your temperature and keep other body functions. Because your body loses water through breathing, sweating, and digestion, it is 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 where you live, how you are physically active, and if you are the victim of a disease or other health problem.