Water composes a significant portion of human body mass and weight. However, the exact percentage of water related to body mass varies amongst individuals. This variation is mostly due to the difference in body fat content between people.
Different types of tissue contain different percentages of water. Every individual's composition of muscle, bone, organ and fat tissues are different. Therefore everyone's percentage of water composition is different to some degree.
Different types of tissue have different percentages of average water content. Blood averages 85 percent water, muscle is 75 percent, bone is 22 percent, the brain is 70 percent and the lungs nearly 90 percent water. Fat tissues can be as little as 10 to 14 percent.
While water composition generally fluctuates between 45 and 75 percent of body weight, the average for an adult male is 60 percent, while an adult female averages 55 percent. Females, on average, naturally have a greater percentage of body fat.
Different methods are used to determine water composition within the body. The simplest is using the average of 60 percent of body weight, but due to fluctuations in fat percentages this is not always accurate. Bioelectrical impedance analysis and dilution and equilibration are two laboratory tests to more accurately measure body water percentage.
The loss of the body water component of body fluid is known as dehydration (References 1). This is a dangerous condition which, if severe enough, can cause death. Many weight-loss products claim to remove excess water weight, but if used too much these products can actually result in dehydration.