Effects of quality of energy intake on growth and metabolic response of enterally fed low-birth-weight infants

Carbohydrate and fat may vary in their ability to support protein accretion and growth. If so, variations in the source of nonprotein energy might be used to therapeutic advantage in enterally fed low-birth-weight infants. To test the hypothesis that high-carbohydrate diets are more effective than i socaloric high-fat diets in promoting growth and protein accretion, low-bir thweight infants weighing 750-1600 g at birth were randomized in a double b lind study to receive one of five formulas differing only in the quantity a nd quality of nonprotein energy. Groups 1, 2, and control received 130 kcal . kg(-1).d(-1) with 35, 65, and 50% of the nonprotein energy as carbohydra te. Groups 3 and 4 received energy intake of 155 kcal . kg(-1).d(-1) with 3 5 and 65% of the nonprotein energy as carbohydrate. Protein intake of all g roups was 4 g . kg(-1).d(-1). Growth and metabolic responses were followed weekly, and macronutrient balances including 6-h indirect calorimetry were performed biweekly. Greater rates of weight gain and nitrogen retention wer e observed at high-carbohydrate intake compared with high-fat intake at bot h gross energy intakes. Greater rates of energy storage and an increase in skinfold thickness were observed in group 4 (high-energy high-carbohydrate diet) despite higher rates of energy expenditure. These data support the hy pothesis that at isocaloric intakes, carbohydrate is more effective than fa t in enhancing growth and protein accretion in enterally fed low-birth-weig ht infants. However, a diet with high-energy and high-carbohydrate content also results in increased fat deposition.