If total body water is known from using antipyrine or other marker, then the formula of Pace and Rathbun can be used to estimate the lean body mass. Water was found to constitute 72.4% of the fat-free (lean) body mass.

lean body mass =

= (total body water ) / (percentage of lean body mass as total body water) =

= (total body water ) / (0.73) =

= (total body water) * 1.37


This is a rearrangement of the equation:


total body water as percent of lean body weight =

= (total body water) / (lean body mass) * 100%


If the equation is rearranged:


total body water in liters =

= (0.73 * (lean body weight in kg))

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