This study examines how body water distribution changes with age. Using a non-invasive body composition device (bioelectrical impedance analysis), researchers measured the amount of water inside and outside the body's cells, both for the whole body and separately for the arms, trunk, and legs, in adults aged 18 to 83. The study explores whether the balance between water inside and outside cells shifts as people get older, independent of their body weight, and whether this pattern differs between men and women or between different parts of the body.