Influence of energy source upon body composition in patients receiving intravenous nutrition

The influence of energy substrate upon body composition was investigated by measuring changes in the body composition of 24 patients who received intravenous nutrition for 2 weeks. The patients were randomly allocated to two groups. Twelve patients (the "glucose group") received all 'nonprotein' calories as glucose, the remaining 12 (the "fat-glucose group") received 60% of 'nonprotein' calories as fat emulsion (Intralipid). Amino acids (FreAmine II) were supplied to give a calorie/nitrogen ratio of 150:1. Total calories were supplied at a rate of 1.4 times the measured resting energy expenditure of each patient. Body composition was measured using routine anthropometric techniques and in vivo neutron activation analysis. Significant increases in body fat and total body potassium (TBK) were recorded in the glucose group, but there was no significant change in total body water (TBW) or total body nitrogen (TBN) in either group. The initial value of the ratio of TBK:TBW had a significant negative correlation with the change of TBK in both groups, and with the change of TBN in the glucose group. The study demonstrates the importance of considering nutritional status when analyzing the effects of intravenous nutrition. Glucose as the sole source of calories induced an increase in body potassium independent of protein synthesis; this effect was not observed in patients who received 60% of their energy supply as lipid emulsion.