Medium- versus long-chain triglycerides for 27 days increases fat oxidation and energy expenditure without resulting in changes in body composition in overweight women.

OBJECTIVE: To determine the effects of long-term consumption of medium chain (MCT) versus long chain triglycerides (LCT) on energy expenditure (EE), substrate oxidation and body composition. HYPOTHESIS: MCT consumption will not result in greater EE, substrate oxidation, and body weight loss compared with LCT consumption. RESEARCH METHODS AND PROCEDURES: Seventeen healthy obese women participated in this randomized, crossover inpatient trial. Meals were prepared and consumed on site for two periods of 27 days. Diets containing 40% of energy as fat, with treatment fat comprising 75% of the total fat, were designed to supply each subject with their individual weight-maintaining energy needs. The MCT diet contained 67% of treatment fat as MCT oil (49% octanoate, 50% decanoate) whereas the LCT diet contained exclusively beef tallow as treatment fat. Body composition was assessed by magnetic resonance imaging (MRI) on day 1 and 28 of each phase while energy expenditure was measured on day 2 and 27. RESULTS: Changes in total and subcutaneous adipose tissue volumes following consumption of MCT and LCT were not different (-0.61+/-0.38 l vs -0.54+/-0.48 l and -0.58+/-0.35 l vs -0.48+/-0.40 l, respectively). Average EE and fat oxidation were greater (P<0.05) during MCT than LCT consumption (0.95+/-0.019 vs 0.90+/-0.024 kcal/min, respectively, for EE and 0.080+/-0.0026 vs 0.075+/-0.0022 g/min, respectively for fat oxidation). DISCUSSION: These results show that long-term consumption of MCT enhances EE and fat oxidation in obese women, when compared to LCT consumption. The difference in body composition change between MCT and LCT consumption, although not statistically different, was consistent with differences predicted by the shifts in EE. It can be concluded that substitution of MCT for LCT in a targeted energy balance diet may prevent long-term weight gain via increased EE.

Modulation of plasma lipid levels and cholesterol kinetics by phytosterol versus phytostanol esters.

It has been suggested that phytosterol and phytostanol esters possess similar cholesterol-lowering properties, however, whether mechanisms responsible are identical has not been addressed. To address this question, cholesterol plasma levels, absorption, biosynthesis, and turnover were measured in 15 hypercholesterolemic subjects consuming prepared diets each over 21 d using a cross-over design. Diets contained either i) margarine (M), ii) margarine with phytosterol esters (MSE) (1.84 g/d), or iii) margarine with phytostanol esters (MSA) (1.84 g/d). Cholesterol absorption was measured using the ratio of [(13)C]cholesterol(oral):D(7)-cholesterol(IV); biosynthesis using D incorporation from D(2)O and turnover by D(7)-cholesterol(IV) decay rates. Plasma total cholesterol level at d 21/22 was lower (P < 0. 05) for MSE (13.4%) but not MSA (10.2%) versus M (6.0%) diets. Plasma low density lipoprotein-cholesterol (LDL-C) mean reductions at d 21/22 were larger (P < 0.05) for MSE (12.9%) and MSA (7.9%) compared with M (3.9%). Plasma TG and high density lipoprotein-cholesterol (HDL-C) levels did not differ across diets. Cholesterol absorption was reduced (P < 0.05) 36.2 and 25.9% at d 21 for MSE and MSA versus M, while cholesterol biosynthesis was reciprocally increased (P < 0.05) 53.3 and 37.8% for MSE and MSA versus M, respectively. Cholesterol turnover was not influenced by diet. These data indicate that plant sterol and stanol esters differentially lower circulating total and LDL cholesterol levels by suppression of cholesterol absorption in hypercholesterolemic subjects.