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BACKGROUND: Oleic acid (OA) is oxidized more rapidly than is palmitic acid (PA). OBJECTIVE: We hypothesized that changing the dietary intakes of PA and OA would affect fatty acid oxidation and energy expenditure. DESIGN: A double-masked trial was conducted in 43 healthy young adults, who, after a 28-d, baseline, solid-food diet (41% of energy as fat, 8.4% as PA, and 13.1% as OA), were randomly assigned to one of two 28-d formula diets: high PA (40% of energy as fat, 16.8% as PA, and 16.4% as OA; n = 21) or high OA (40% of energy as fat, 1.7% as PA, and 31.4% as OA; n = 22). Differences in the change from baseline were evaluated by analysis of covariance. RESULTS: In the fed state, the respiratory quotient was lower (P = 0.01) with the high OA (0.86 +/- 0.01) than with the high-PA (0.89 +/- 0.01) diet, and the rate of fat oxidation was higher (P = 0.03) with the high-OA (0.0008 +/- 0.0001) than with the high-PA (0.0005 +/- 0.0001 mg x kg fat-free mass(-1) x min(-1)) diet. Resting energy expenditure in the fed and fasting states was not significantly different between groups. Change in daily energy expenditure in the high-OA group (9 +/- 60 kcal/d) was significantly different from that in the high-PA group (-214 +/- 69 kcal/d; P = 0.02 or 0.04 when expressed per fat-free mass). CONCLUSIONS: Increases in dietary PA decrease fat oxidation and daily energy expenditure, whereas decreases in PA and increases in OA had the opposite effect. Increases in dietary PA may increase the risk of obesity and insulin resistance. Copyright © 2005 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]

We hypothesized that there is less suppression of whole-body protein breakdown with feeding in patients with cystic fibrosis (CF) who exhibit decreased insulin secretion after a single meal. Using [1-(13)C]leucine, we measured rates of nonoxidative leucine disappearance (whole-body protein synthesis) and protein breakdown in nine CF patients (6-11 y of age) and five healthy control subjects (8-10 y of age) during feeding and fasting. In the CF patients, synthesis and breakdown (mean +/- SD) were 172 +/- 61 and 157 +/- 67 miromol x kg-1x h-1 during feeding and 140 +/- 24 and 178 +/- 26 micromol kg-1 h-1 during fasting. The respective control values were 129 +/- 27 and 114 +/- 20 micromol kg-1 h-1 during feeding and 136 +/- 13 and 173 +/- 18 micromol x kg-1 x h-1 during fasting. Leucine balance was nearly identical in the two groups. By analysis of variance, there was a significant effect of feeding on protein breakdown but no difference between the groups. However, when each group was analyzed separately, feeding resulted in a 34% decrease in breakdown in the control subjects (P = 0.001) and a 23% increase in synthesis in the CF group (P = 0.058). Plasma insulin concentrations did not differ in the two groups. Thus, feeding may affect protein turnover differently in children with CF than in control children independently of plasma insulin concentration. (c) 1996 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]