Tanita s body water monitor scales use Bioelectric Impedance Analysis (BIA) the same accurate technology used for body fat monitoring. BIA passes freely through the fluids contained in muscle tissue and in blood but it encounters difficulty when passing through fat tissue which contains little water. By using the impedance reading gender height and weight the scale can quickly and reliably calculate body fat and total body water percentages. Proper hydration is essential for life. Maintaining a healthy body water% improves all overall health and keeps you feeling energized and operating at a peak performance. As a general guideline the average TBW% ranges for a healthy adult are: Female 45 to 60% Male 50% to 65%.