Structured medium and long chain triglycerides show short-term increases in fat oxidation, but no changes in...

Medium chain triglycerides (MCT) have been suggested as modulators of human energy expenditure (EE) and thus may influence total and regional body fat distribution.

To investigate in overweight men the effects of structured medium and long chain triglycerides on EE, substrate oxidation and body adiposity, compared to extra virgin olive oil (OO).

In a 6 week single-blind crossover study, 23 overweight men were randomly assigned to consume a standard high-fat diet of which 75% total fat was provided as either structured medium and long chain triglycerides referred to as structured oil (StO), or OO. EE and body composition were measured using indirect calorimetry and magnetic resonance imaging, respectively, at weeks 1 and 6 of each phase.

Body weight decreased (p<0.01) from baseline to end-point during consumption of both the StO (-1.46+/-0.4k g) and OO (-1.17+/-0.4 kg); however, no significant treatment differences were observed. There were no changes in body composition among treatment groups. No differences between diets for EE measurements were reported. Fat oxidation rates did not differ between oils, but were reduced (p<0.05) in the StO group between baseline (0.0020+/-0.0003 g/kg fat free mass per min) in comparison to after week 6 (0.0013+/-0.0001 g/kg fat free mass per min). No differences in carbohydrate oxidation rate were noted across diets or time.

The present structured medium and long chain triglyceride oil increases short-term fat oxidation but fails to modulate body weight or adiposity through a change in EE.