Effect of glucose to fat ratio on energy substrate disposal in children with cystic fibrosis fed enterally

High fat containing diets lower VCO2 in patients with impaired pulmonary fu nction fed at a high level of energy intake. We tested the effect of a high fat enteral nutrition on VCO2 and substrate oxidation in cystic fibrosis p atients fed enterally 130% RDA. VCO2 and substrate oxidation were studied i n a group of eight 6-19 year old patients while receiving for 1 month and i n a random order isocaloric (1000 kcal/m(2)), isonitrogenous enteral diet w ith a normal fat and a high fat content (40% and 67% of non-protein energy intake). Substrate oxidation and net balance were estimated using indirect calorimet ry at the end of each study period. Overnight high fat enteral infusion res ulted in no significant change in VCO2 and VO2 but lowered RO (0.84 +/- 0.0 1 vs 0.88 +/- 0.01, P = 0.02) and non-protein RQ (0.83 +/- 0.01 vs 0.88 +/- 0.01). In spite of a higher glucose oxidation rate (8.1 +/- 0.5 vs 6.3 +/- 0.5 g, h(-1), P = 0.04), glucose net balance was significantly higher duri ng normal fat formula administration (+2.5 +/- 0.8 v -0.3 +/- 0.7 g/h, P < 0.05). The present study failed to show any benefit of a high fat diet on VCO2 in non oxygenodependant cystic fibrosis children and adolescents fed slightly above RAD. Normal fat enteral formula led to higher glycogen repletion. (C) 1999 Harcourt Publishers Ltd.