Energy requirements for growth and development in infancy.

Current international recommendations for energy requirements are based on >9000 measurements of energy intake in both breast- and formula-fed infants. The measurement of energy intake in babies is far from straightforward and the possibility of significant error is great. The opportunity now exists, however, to compare current recommendations with measurements of total energy expenditure (TEE) obtained via the doubly labeled water technique. Approximately 300 measurements of TEE in the first year of life have been made in normal, healthy babies. These data show that estimates of energy intake derived from the measurements of TEE are considerably below the current international recommendations. The same technique has also allowed the energy requirements of sick infants to be evaluated. Two examples are highlighted of infants born small for gestational age and infants born with cystic fibrosis. First, data collected from babies born small for gestational age suggest that such infants have a TEE and hence requirement approximately 20% above that found in infants born with a weight appropriate for their gestational age. This information will be relevant to those professionals attempting to supply optimum nutrition to babies born small for gestational age. Second, in cystic fibrosis it has been suggested that, concurrent with the basic features of the disease, there is an energy-wasting lesion that will increase TEE and hence energy requirement. Recent data collected from babies with cystic fibrosis strongly suggest that this is not the case, and previous data were confounded by subclinical disease status.