Body water content is the total amount of water present in a person’s tissues, normally around 50 to 70 percent of body weight depending on age, sex, and the ratio of lean to fat tissue. It divides into intracellular fluid, which bathes the inside of cells, and extracellular fluid, which includes blood plasma, lymph, and the fluid surrounding cells. Water is the medium for virtually all biochemical reactions, carries nutrients and metabolic waste, and regulates core temperature through sweating. In nutrition, body water content underpins hydration guidance, the formulation of oral rehydration solutions, and the interpretation of bioelectrical impedance results, since fat-free mass holds proportionally more water than adipose tissue.