Energy expenditure measurements in relation to energy requirements

Long-term good health for weight-stable adults requires balance between energy intake (EI) and energy expenditure (EE). Both EI and EE measurements can be used to estimate energy requirement. Results from studies conducted at Beltsville Human Nutrition Research Center in which two or more methods were used to measure EE are compared to determine relative differences in measurement techniques. Comparison of EI estimated from dietary intake records (7 d minimum) with EI measured in 12 controlled feeding studies (45 d minimum) in 266 subjects indicated that diet records underestimate energy requirement by 18%. Comparison of EE measured in a room calorimeter and by doubly labeled water (2H(2)18O) in nine subjects showed no significant difference between methods within the calorimeter environment (1.6 +/- 2.6%) but free-living EE measured by 2H(2)18O was greater (13.2 +/- 7.1%) due to physical activity. Comparison of metabolizable energy (ME) intake, 2H(2)18O, and direct or indirect calorimetry in four subjects indicated no difference between ME and EE measured by 2H(2)18O (-1.0 +/- 1.3%) or between direct and indirect calorimetry (0.6 +/- 0.9%); however, free-living EE measured by 2H(2)18O was greater than the value calculated by calorimetry (15.3 +/- 5.0%). Each method has associated limitations that include availability, accuracy, precision, and cost. Appropriate application and interpretation of results for all methods are essential.