Measurement of Body Potassium With a Whole-Body Counter: Relationship Between Lean Body Mass and Resting Energy Expenditure

We conducted studies to determine whether the Mayo whole-body counter could be used to measure body potassium, and thus lean body mass (LBM), and whether moderate obesity alters resting energy expenditure when corrected for LBM. Twenty-four nonobese and 18 moderately obese adults underwent body potassium (⁴⁰K) counting, as well as tritiated water space measurement and indirect calorimetry. LBM values predicted from ⁴⁰K counting and tritiated water space measurements were highly correlated (P = 0.0001; r = 0.88). Resting energy expenditure was closely related to LBM (P<0.0001; r = 0.78): kcal/day = 622 kcal + (LBM ċ 20.0 kcal/kg LBM). In this relationship, the obese subjects did not differ from nonobese subjects. In summary, the Mayo whole-body counter can accurately measure LBM, and moderate obesity has no detectable effect on corrected resting energy expenditure.