You need water to keep your metabolism working properly. In order for this to happen, there is a certain level of water in each of our bodies that we need to maintain. If we don't keep that amount, our bodies will start to dehydrate. An easy way to think of it is to think of your car's need for oil. If your oil level gets too low, your engine will start to run rough. If you totally deplete your oil supply in your car, your engine will stop running. Same with your body. Therefore it is easy to see why it is very important to drink six to eight glasses of water a day.