Fatty acids are classified as medium length if they have carbon chains of between 6 and 12. Triglycerides composed predominately of this length of fatty acids are designated as medium chain triglycerides (MCTs) and have medicinal uses in individuals with malabsorption, malnutrition and hyperlipidaemia. Evidence suggests that MCT are metabolised differently to the longer chain triglycerides (LCTs) that predominate in the normal mixed diet. Generally, MCTs are oxidised by the liver and as such are known to increase postprandial thermogenesis, when compared to LCTs. Therefore MCTs are of interest because they may be beneficial to those wishing to lose weight. However, although it is known that MCT have an effect on thermogenesis in healthy normal weight individuals, it is not known if they can cause a thermogenic effect in obese individuals.
The thermic effect of MCTs has been investigated by researchers1 who fed 6 lean subjects and 6 obese subjects a mixed meal containing either 38 grams of LCTs or 30g of MCT plus 8g of LCTs. The results showed that the postabsorptive resting metabolic rate was higher in the obese subjects compared to the normal weight subject following both types of meal. Following ingestion of food, heat production increased in all subjects for the subsequent 6 hours, but was higher in both groups following ingestion of the MCT meal compared to the LCT meal. There was also an significantly greater increase in the resting metabolic rate following the MCT meal in both groups compared to the LCT meal. Medium chain triglycerides therefore appear to have a benefit in obese individuals because of their inefficient use by the body, whereby the contribute to the bodies energy requirements by oxidation to ketone bodies.
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