Objective: To determine whether medium-chain triglycerides, in low-to-moderate amounts consumed with meals (at breakfast, lunch and dinner), can increase daily energy expenditure (EE) and 24-h urinary excretion of catecholamines in humans.
Design: Dose-response study conducted under double-blind randomised design.
Setting: Respiratory chamber at the Faculty of Medicine, University of Geneva.
Subjects: Eight healthy young men were recruited from the student population by advertisement in our Faculty.
Methods: 24-h EE and urinary catecholamines were measured in each subject during stay in a respiratory chamber on four separate occasions. These were randomised between four different combinations of medium-chain triglycerides (MCT) and long-chain triglycerides (LCT), a total 30g/day, which was consumed with their habitual diet in three equal parts (10g each) at breakfast, lunch, and dinner in the following ratio of MCT: LCT (g/g) 0:30, 5:25, 15:15 and 30:0.
Results: 24-h EE increased significantly with increasing MCT:LCT ratio (ANOVA, P < 0.001), with the diet providing a total of 15-30 g MCT per day stimulating 24-h EE by 5%: this corresponds to a mean absolute increase in daily EE of approximately 500kJ, with individual values varying between 268 kJ and 756 kJ. No significant differences were observed in respiratory quotient nor in urinary nitrogen losses across diets, but 24-h urinary noradrenaline was significantly increased (ANOVA, P < 0.025), whereas adrenaline and dopamine were unaltered.
Conclusions: This study suggests that relatively low-to-moderate intake of MCT (15-30 g per day) as part of habitual diet may play a role in the control of human body composition by enhancing daily EE, and that this effect is mediated at least in part through activation of the sympathetic nervous system.