The medium chain triglycerides (MCT) are special types of saturated fats derived from coconut oil and formats of variable length chains ranging between 6 and 12 carbon molecules, which are used by the body in a different way as compared to long chain fatty acids (LCT) and fats that are more abundant in nature. The long chain triglycerides are fat reserves both in humans and in plants and their length varies between 18 and 24 carbon molecules.
The medium chain triglycerides are a source of easily available energy and they are commonly used to lose weight . Unlike ordinary fat, medium chain triglycerides are not fattening: They promote weight loss by increasing the rate of calorie burning (thermogenesis). Long chain triglycerides, however, are usually stored as fat deposits and, as their energy is stored, a diet rich in fat does nothing but reduce the metabolic rate. The reason of the difference with which the organism metabolises MCT and LCT resides in their size. The long chain triglycerides, are difficult to metabolise for the organism, and thus these are stored. The medium chain triglycerides, however, are rapidly burned for energy and therefore also support combustion of LCT.
In circulation, medium chain triglycerides (MCT) are available as food supplements. Several companies add orange flavour. There are also products having butter or olive oil flavours that can be used as a salad dressing on dough.
The medium chain triglycerides promote thermogenesis. One study compared the thermogenic effect of a high-calorie diet containing 40% of MCT type fat with one containing 40% of LCT type fat. The thermogenic effect (calories lost six hours after a meal) of MCT was approximately twice that of LCT: 120 calories against 66. Researchers concluded that the excess energy provided by fat in the form of medium chain triglycerides is not stored effectively as fat and is burned. A follow-up showed that MCT oil administered for a 6 day period increases diet-induced thermogenesis by 50% .
In another study, researchers compared individual meals of 400 calories each, composed entirely of MCT and LCT.  The thermogenic effect of MCT over 6 hours was three times greater than that of LCT. In addition, while long chain triglycerides increased serum levels of fat by 68%, medium chain triglycerides had no such effect on blood fats. The researchers concluded that, for equal calories taken, a replacement of LCT with MCT causes a weight loss.