Components of total energy expenditure in healthy young women are not affected after 14 days of feeding with medium- versus long-chain triglycerides

Objective: To examine the effect of consumption of medium-chain triglycerid es (MCT) vs. long-chain triglycerides (LCT) on total energy expenditure (TE E) and its components in young women during the second week of a 2-week fee ding period. Research Methods and Procedures: Twelve healthy lean women (age: 22.7+/-0.7 years, body mass index [BMI]: 21.5+/-0.8 kg/m(2)) were fed weight maintena nce diets containing 15% of energy as protein, 45% as carbohydrate, and 40% as fat, 80% of which was treatment fat, for 2 weeks in a randomized cross- over design separated by a 2-week washout period. Dietary fat was composed of triglycerides containing either 26% medium-chain fatty acids (MCFA) and 74% long-chain fatty acids (LCFA), or 2% MCFA and 98% LCFA. Free-living TEE was measured from day 7 to 14 on each dietary treatment using doubly label ed water (DLW). Basal metabolic rate (BMR) and thermic effect of food (TEF) were measured on days 7 and 14 using respiratory gas exchange analysis (RG E) for 30 minutes and 330 minutes, respectively. Activity-induced energy ex penditure (AIEE) was derived as the difference between TEE and the sum of B MR and TEF. Results: The average TEE while consuming the MCT diet (2246+/-98 kcal/day) did not differ from that of the LCT diet (2186+/-138 kcal/day. BMR was sign ificantly higher on the MCT diet on day 7 (1219+/-38 kcal/day vs. 1179+/-42 kcal/ day): but not on day 14; there was no effect of diet on TEF. There w ere no differences in BMR, TEF, or AIEE between diets when expressed as per centages of TEE. On average, BMR, TEF, and AIEE represented 54.6%, 8.2%, an d 37.2%, respectively, of TEE. Discussion: Results suggest that between day 7 and day 14 feeding of MCT vs . LCT at these levels, TEE is not affected and that increases seen in energ y expenditure following MCT feeding may be of short duration. Thus, compens atory mechanisms may exist which blunt the effect of MCT on energy componen ts over the longer term.