title: Longitudinal studies on metabolic rate, heat loss, and energy cost of growth in low birth weight infants.
abstract: Longitudinal studies on total and resting metabolic rate and total heat loss were made in 14 LBW infants, age 1-58 d. Metabolic rate was calculated from indirect calorimetry, heat loss was measured by direct calorimetry. Total metabolic rate and total heat loss were lowest during the first week of life, 178.9 +/- 18.0 and 171.8 +/- 15.5 kJ X kg-1 X 24 h-1, respectively. During the age period of 8-58 d both total metabolic rate and heat loss showed a very slight increase with age: mean total metabolic rate was 278.8 +/- 2.6 and mean total heat loss 257.0 +/- 3.4 kJ X kg-1. during the first week of life and 248.0 +/- 2.5 during d 8-58. The energy cost of components of new tissue was calculated from the energy balance equation. Ecomponents during the second week of life was 25.5 +/- 4.9 kJ/g weight gain and 11.9 +/- 0.4 kJ/g weight gain over subsequent weeks. The net energy cost of tissue synthesis, calculated from the difference between indirect and direct calorimetry was 3.2 +/- 1.1 kJ/g weight gain during the second week and 1.1 +/- 0.1 kJ/g weight gain in the following weeks. A neonate who receives a caloric intake of 535 kJ X kg-1 X 24 h-1 and is growing at a rate of 17 g X kg-1 X 24 h-1 will use 42% of the caloric intake for maintenance and thermoregulation, 6% for activity, 38% for the components of new tissue, 4% for tissue synthesis and 10% for loss in faeces and urine.
mesh_terms: D001833:Body Temperature Regulation; D001835:Body Weight; D002151:Calorimetry / Q000379:methods; D002149:Energy Intake; D004734:Energy Metabolism; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008660:Metabolism