1. Introduction

A literature search over the past decade reveals very few papers containing new data on energy expenditure during infancy. This is largely due to the difficulty of performing the necessary measurements in any circumstances other than when children are asleep. Torun discusses the problems in detail elsewhere in this volume and points out the limitations of attempting to predict total energy expenditure of children by the factorial method (TORUN, 1990). Similarly, Spurr describes the use of heart-rate monitoring and its limitations in very young children for whom calibrations cannot be obtained (SPURR, 1990).

The development of the doubly-labelled water method for use in man has removed these limitations and promises to revolutionise our concepts of energy metabolism and requirements in these age groups. This paper provides a description of the new method and a review of the results obtained so far.