Effect of replacing glucose with lipid on the energy metabolism of newborn infants.

1. Indirect calorimetry and primed constant infusion of [U- 13 C]glucose were combined in 28 appropriate-for-gestational age newborn, parenterally fed infants, in order to measure glucose utilization and glucose oxidation and to estimate lipogenesis from glucose. 2. The infants were randomly allocated to either a group receiving glucose as the non-protein energy source or a group having one-quarter of the glucose energy replaced by intravenous fat. The energy intake (370 kJ day −1 kg −1 ) and protein intake (3.4 g day −1 kg −1 ) were similar in both groups. 3. Energy expenditure ( P P P 4. The significant excess of glucose utilization over oxidation ( P 5. Fat synthesis from glucose was higher in the glucose/amino acid group ( P P 6. As lipogenesis from glucose is an energy- and oxygen-consuming and a carbon dioxide-producing process, the data suggest that the differences between the glucose-only group and the lipid-supplemented group are due to different rates of lipogenesis from glucose.