INFLUENCE OF HUMAN OBESITY ON THE METABOLIC-FATE OF DIETARY LONG-CHAIN AND MEDIUM-CHAIN TRIACYLGLYCEROLS

The metabolic fate of an oral long-chain-triacylglycerol (LCT) load an d of a mixed oral LCT and medium-chain-triacylglycerol (MCT) load was followed for 6 h in eight control and eight obese subjects with normal postabsorptive triacylglycerol concentrations. Labeled triacylglycero l and indirect calorimetry were used. Results showed that LCTs were le ss oxidized in obese than in control subjects (3.2 +/- 0.5 compared wi th 6.0 +/- 0.4 g, P < 0.01). Moreover, the amount of LCT oxidized was negatively correlated with fat mass (r = -0.77, P < 0.01). Appearance in plasma of dietary triacyglycerol-derived long-chain fatty acids was blunted in obese subjects and it was negatively related to fat mass ( r = -0.84, P < 0.01) and positively to LCT oxidation (r = 0.70, P < 0. 01). On the contrary, MCT oxidation was not altered in obese subjects compared with control subjects. Furthermore, the proportion of MCTs ox idized was higher in both groups compared with LCTs ((x) over bar +/- SEM: 57.5 +/- 2.6% compared with 15.2 +/- 1.6%, P < 0.01, n = 16). Our conclusion is that obesity is associated with a defect in the oxidati on of dietary LCTs probably related to an excessive uptake by the adip ose tissue of meal-derived long-chain fatty acids. MCTs, the oxidation of which is not altered in obesity, could therefore be of interest in the dietary treatment of obesity.