Energy Expenditure in Extremely Low Birth Weight Infants Near Time of Hospital Discharge

Objective

To test the hypothesis that total energy expenditure is significantly higher in extremely low birth weight (ELBW) infants compared with healthy term infants near the time of discharge.

Study design

This study was designed to determine total energy expenditure and body composition in a group of ELBW infants nearing discharge receiving full-volume enteral feedings of fortified breast milk or postdischarge formula (Neosure) (n = 10; mean birth weight, 0.8 ± 0.1 kg; mean gestational age, 26 ± 0.8 weeks; mean age at study, 68 ± 9 days; mean postconceptional age, 36 ± 1 weeks) and compare them with healthy term newborns all receiving breast milk (n = 14; mean birth weight, 3.5 ± 0.5 kg; mean gestational age, 39.0 ± 1.4 weeks; mean age at study, 2.3 ± 1 days). Body composition and total energy expenditure were measured using the doubly labeled water method over a 7-day period.

Results

Mean total energy expenditure was significantly higher in the ELBW infants compared with the term infants (89 ± 22 kcal/kg/day vs 58 ± 19 kcal/kg/day; P ≤ .001). Total energy expenditure normalized to fat-free mass was also significantly greater in the ELBW infants (98 ± 3 kcal/kg/day vs 73 ± 20 kcal/kg/day; P ≤ .01).

Conclusions

The rate of total energy expenditure is greater in ELBW infants nearing discharge compared with normal healthy term infants. In the ELBW infants, higher energy intake compensates for their higher total energy expenditure.

Abbreviations: DLW, Doubly labeled water, ELBW, Extremely low birth weight