Abstract

The development of the doubly-labelled water method for use in humans provides nutritionists with the first non-invasive means of assessing total habitual energy expenditure in free-living infants and children. In combination with other more classical techniques of indirect calorimetry and assessment of body composition the new method is offering new insights into the partition of energy between maintenance metabolism, physical activity and growth. This paper describes the technique and considers its advantages and limitations with particular reference to its use in children. The accuracy of the method has been extensively tested in cross-validation studies involving adults, but there are only two reported validation studies in infants and one in premature babies. These suggest that the method is accurate, but there is a need for further validation. There are 12 published reports of DLW studies in childhood which include approximately 500 different measurements. The salient findings from these studies are summarised. Optimal uses of the new technique in studies of energy metabolism in infants and children are discussed. The new method is likely to play an important role in the establishment of new recommendations for energy requirements.