Water weight, your body is not only made up of muscle, bones, and organs, but also soft tissue and water. About 20-30% water. Your body uses this liquid to help hydrate itself, allow for cooling (sweating), and assist in the breakdown of food in the digestive system. No one can live without water. your muscles need it to maintain flexibility, and your body needs it to maintain hydration. Dehydration is lack of fluid in the body, this can lead to heat exhaustion and heat stroke, or death.