Objective Measures for the Assessment of Energy Expenditure: A Historical Overview

Accurate measurement of energy expenditure and estimate physical activity is extremely important in terms of health outcome and effectiveness of intervention programs. However, total energy expenditure, apart from physical activity, includes basal energy expenditure and food thermogenesis. Energy expenditure can be determined objectively by criterion methods, using direct and indirect calorimetry and doubly labeled water (DLW). Indirect calorimetry is frequently applied in laboratory settings, while DLW is the reference for energy expenditure under free-living conditions. These techniques have been used in both clinical and research settings. This review includes a historical overview of these techniques, with more emphasis on the indirect calorimetry and DLW, with particular reference to their validity. These criterion methods are the most valid and reliable measurements against which all other energy expenditure assessments methods should be validated. However, they have important limitations, which are addressed in the present review. The preferred method to determine energy expenditure is likely to depend principally on the number of study participants to be monitored, the time of measurements and the finances available. New technologies have evolved, such as accelerometry, and additional studies are needed to examine the accuracy of these methods and the possibility of improving the accuracy of measurement by combining two methods or more.