Metabolic consequences of increasing energy intake by adding lipid to parenteral nutrition in full-term infants.

The effect on energy metabolism and fuel util- ization of increasing energy intake by adding intravenous lipid to a glucose and amino acid regimen was examined. Twenty full- term, appropriate-for-gestational-age, intravenously fed neonates were entered into one of two groups: total energy intake was 261 Id . kg' .d1 (62kcal .kg1 .d1) ingroup1and355kJ. kg' . (85 kcal kg' . d') in group 2. Both groups received 2.8 g pro- teinkg� . dand 14 g glucose . kg1 . d'. Group 2 received an additional 2 g lipid . kg1 . d'. Metabolic rate, respiratory gas exchange, and nonprotein substrate oxidation were similar in both groups. The addition of energy as lipid enhanced nitrogen retention (230 vs 306 mg kg1 . d1; P < 0.02) and utilization (52.8% vs 66.5%; P < 0.03). Our data suggest that nitrogen utilization is improved in parenterally fed neonates by adding fat and increasing energy intake without change in metabolic rate, carbon dioxide production, oxygen consumption, and nonprotein substrate utilization. Energy expenditure does not necessarily in- crease with increasing energy intake independently of diet composition. Am J Clin Nutr 1994;59:659-62.