The total body water (TBW) in an average adult male constitutes about 60% of body weight. This is because water is a major component of intracellular and extracellular fluids, essential for maintaining cell function and homeostasis. Understanding TBW is crucial in clinical settings like fluid management during surgery or treating dehydration. Variations exist based on age, sex, and body composition, but 60% is the standard approximation for a healthy adult male. Accurate assessment of TBW helps guide appropriate intravenous fluid administration and electrolyte replacement.

Reference: Guyton and Hall Textbook of Medical Physiology, John E. Hall, 13th Edition.