Measurement of energy expenditure

Background At the present state of the art, energy expenditure is measured with indirect calorimetry, where energy production is calculated from oxygen consumption, carbon dioxide production and urine-nitrogen loss. Daily energy expenditure consists of three components, i.e. maintenance expenditure, diet-induced energy expenditure and activity-induced energy expenditure. Key Methods Indirect calorimetry methods for the assessment of gaseous exchange as presented in this chapter include a mouthpiece or facemask, ventilated hood, respiration chamber and doubly labelled water. Designing studies to evaluate intervention effects on energy expenditure, including drugs, should be based on the energy expenditure component as targeted. The indicated method for the measurement of maintenance expenditure is a ventilated hood. Diet-induced energy expenditure can be measured with a ventilated hood or in a respiration chamber. Activity-induced energy expenditure is measured under standardised conditions with a mouthpiece, facemask or in a respiration chamber and under free-living conditions with doubly labelled water. Energy expenditure can be estimated and evaluated with alternative methods including prediction equations for maintenance expenditure, based on height, weight, age and gender; doubly labelled water validated accelerometers to assess activityinduced energy expenditure; and measurements of food intake as evaluated with the doubly labelled water technique.