How much water is in the body?

Water makes up approximately 60% of your total body composition. In addition, 73% of lean body mass or muscle is composed of water. It is the essential nutrient for survival and is required for all cell functions. Water is also an important constituent in thermoregulation, because it is a major component of blood volume. It is mainly lost through sweat, respiration, and waste. However, when the body is dehydrated, most of the water lost is from the blood.