Effects of dietary fat on postprandial substrate oxidation and on carbohydrate and fat balances.

Abstract

To study the effect of dietary fat on postprandial substrate utilization and nutrient balance, respiratory exchange was determined in seven young men for 1 h before and 9 h after the ingestion of one of three different breakfasts: i.e., bread, jam, and dried meat (482 kcal: 27% protein, 62% carbohydrate, and 11% fat); bread, jam, and dried meat plus 50 g of margarine containing long-chain triglycerides (LCT); or bread, jam, and dried meat plus 40 g medium-chain triglycerides (MCT) and 10 g LCI margarine (858 kcal: 15% protein, 35% carbohydrate, and 50% fat).Plasma glucose concentrations peaked 45 min after the start of the meals. When compared with the low fat meal, the LC1T margarine supplement had no effect at any time on circulating glucose and insulin concentrations, nor on the respiratory quotient. When MCIrs were consumed, plasma glucose and insulin concentrations remained lower and plasma FFA concentrations higher during the first 2 h. 9 h after the breakfasts, the amounts of substrates oxidized were similar in each case, i.e., -320, 355, and 125 kcal for carbohydrate, fat, and protein, respectively. This resulted in comparable carbohydrate (mean±SD = -22±32, -22±37, and -24±22 kcal) and protein balances (-7±9, +7±7, and -8±11 kcal) after the low fat, LCT-and MCI-supplemented test meals, respectively. However, after the low fat meal, the lipid balance was negative (-287±60 kcal), which differed significantly (P < 0.001) from the fat balances after the LCT-and MCT-supplemented meals, i.e., +60±33 and +57±25 kcal, respectively. The results demonstrate that the rates of fat and of carbohydrate oxidation are not influenced by the fat content of a meal.

Energy replacement attenuates the effects of prior moderate exercise on postprandial metabolism in overweight/obese men

“…23 For these calculations, urinary nitrogen excretion was assumed to be 0.11 mg kg À1 min À1 throughout all trials, based on data from similar studies in the literature. 24,25 We consider this assumption to be justified as data from previous studies have demonstrated that exercise with similar energy expenditures to the exercise intervention used in the present study, either with or without an energy deficit, does not influence postprandial protein oxidation rates. 25,26,27 The total area under the 8.5 h variable vs time curves (AUC), calculated using the trapezium rule, and the incremental AUC, calculated as the increment in AUC over baseline concentrations, were used as summary measures of the postprandial responses.…”

Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13C isotope ratio mass spectrometry

“…Firstly, high-fat diets have high energy density and secondly, although the exact mechanism is still debated, it has been suggested by some investigators that consumption of high-fat diets leads to hyperphagia (Lissner et al, 1987;Stubbs et al, 1995). A possible third factor could be that dietary fat is mainly stored and not oxidized in the post-prandial period (Flatt et al, 1985;Schutz et al, 1989).…”

Dietary fat composition and human adiposity

“…This association is likely explained by macronutrient imbalance favoring an excess fat intake above fat oxidation. Indeed, there is some evidence that excess dietary fat does not promote its own oxidation (Flatt et al, 1985;Flatt, 1988;Bennett et al, 1992) as does excess intake of carbohydrates (Flatt, 1988). It has also been demonstrated that high fat diets give way to overconsumption because fat seems to have a lesser effect on satiety than do other macronutrients (Blundell et al, 1993).…”