It is well understood that medium chain triglycerides (MCT) have a higher thermogenic effect than long chain tri-glycerides (LCT) and this fact has stimu-lated considerable interest in the possible use of MCT for body fat control. Me-dium chain triglycerides are prepared by the esterification (addition) of medium chain fatty acids (MCFA) to a glycerol backbone. Medium chain fatty acids are themselves naturally occurring in certain tropical oils and are commercially ob-tained from fractionation of coconut oil. Medium chain fatty acids, by definition, contain from six to 10-12 carbon atoms in their hydrocarbon chain, whereas long chain fatty acids are 14 or more carbon atoms in length. Animal fats and most vegetable oils (“typical dietary fats”) are comprised of long chain triglycerides. CapTri® is comprised of mostly pure C8 fatty acids with with some C10s and absolutely no C12s since these can uplink to long chain fats. The difference in physical structure of MCT as compared to LCT (that is, the shorter fatty acid chains) confer different chemical properties to these fat molecules, which results in MCT following a differ-ent metabolic pathway in the body. Con-ventional fats (LCT) are released from the intestines in complex with carrier proteins in special particles called chylomicrons .
Rather than being released directly into the bloodstream, the chylomicrons are released into the lymphatic system and then enter the blood via the thoracic duct. This circulatory route results in the LCT bypassing the liver and instead being cir-culated throughout the body. Capillaries can bind the chylomicrons where they are acted on by an enzyme called lipoprotein lipase, which releases the long chain fatty acids from the chylomicron particle. The long chain fats are then stored in fat cells where they remain (generally) until they are needed as a fuel source. The basic concept is that conventional dietary fat is not utilized immediately as a fuel source but instead is preferentially stored in fat cells. Fat is the biochemical form in which the body stores excess energy. Fat is, in essence, a storage molecule . So it makes sense that dietary fat would be preferentially stored. In contrast, MCT is not incorporated into chylomicrons and instead is absorbed directly into the bloodstream.
It is carried to the liver by the portal vein where it is rapidly metabolized. Several things can happen to MCT in the liver, but the pri-mary metabolic fate is the conversion of MCFAs into ketone bodies. Ketone bod-ies are partially metabolized fatty acids which are then released from the liver into the general circulation. The ketones are then used as an immediate fuel source by peripheral tissues such as muscle. Another important difference between MCFAs and conventional fats is that long chain fats require a transport sys-tem called the carnitine shuttle to enter mitochondria . Mitochondria are special structures inside cells where fats and other substrate molecules are converted into ATP, the form of energy which di-rectly powers cellular work. The carnitine shuttle transports long chain fats from the cytoplasm to the interior of the mitochon-dria, where they are burned as fuel. The activity of the carnitine shuttle is inhib-ited by a metabolic intermediate called malonyl-CoA, which is generated as a byproduct of carbohydrate metabolism.
This means that metabolism of long chain fats occurs only slowly as long as carbo-hydrate is available as a fuel source. Once carbohydrate levels are depleted, there is less malonyl-CoA around and the activity of the carnitine shuttle increases and long chain fats are more readily used as fuel. MCFAs, on the other hand, do not require the carnitine shuttle for transport, so they are rapidly metabolized as fuel even in the presence of carbohydrate. These properties result in MCT behaving very differently from conventional fats in the body. Instead of being preferentially stored as body fat (as are LCT), MCT is preferentially used as fuel with very little MCT being stored as body fat (1-3). Since MCT can be oxidized at the same time as glucose, this alternative fuel source has the potential to spare carbohydrate oxidation. This could delay depletion of muscle glycogen and the onset of fatigue during prolonged endurance exercise. We talked about a study demonstrating this last month . Your total energy expenditure (TEE) is the total number of calories you burn in a day. (See reference 4 for a nice discussion of the components of energy expenditure, especially as relates to food intake and ex-ercise activity.) The biggest component of TEE is the basal metabolic rate, or BMR. This is the number of calories you burn at rest just to maintain life. Things like maintenance of body temperature, blood pressure, heart rate, breathing, nerve transmission, ionic gradients across cell membranes, and things like that account for about 70 percent of the total number of calories the average person burns in a day.
Another significant factor of TEE is the thermic effect of activity (TEA) which basically is energy spent in activity, in-cluding exercise. The next component of your daily energy expenditure is the ther-mic effect of feeding, or TEF. This is es-sentially energy lost as body heat during fuel (food) metabolism. When your car engine burns gasoline some of the energy is converted into useful work—making the car move. Some of the energy from burning the gasoline is simply lost as heat to the environment. You know how hot a car engine gets? A lot of the energy from burning the gasoline is simply lost as heat. All of that energy which heats up the engine and the radiator and the exhaust system is not being used to make the car go— it’s just lost to the environment. What happens inside the human body during fuel metabolism is significantly more complicated, but a general analogy exists. When your body burns food as fuel some of the energy which is produced is captured as ATP and can be used to power the body, but some of it is simply lost as body heat and dissipated into the environ-ment. The proportion of the food energy which is lost as heat during metabolism is the TEF, and it’s different for different foods.
(See “The Biochemistry of Energy Expenditure” by J.P. Flatt in reference 5 for a detailed discussion.) Conventional fats have a TEF around five percent, which means five percent of the calo-ries supplied by the fat are lost as heat. Carbohydrate has a TEF of eight to 10 percent and protein around 20-25 percent . Different fuel substrates (protein, fat, and carbohydrate) follow different metabolic pathways and are converted into ATP with different efficiencies. So it seems logical that some foods might generate more body heat during metabolism than others. Some people think that when it comes to dieting and body weight control that a calorie is a calorie and it doesn’t mat-ter much what you eat. However, since different foods have differing energetic efficiencies it would seem that all calories are not created equal. Several studies in laboratory animals have shown that diets high in MCT result in increased thermogenesis and less depo-sition of body fat than diets high in LCT (1,2,3,6). Studies in humans have simi-larly demonstrated an increase in thermo-genesis after feeding MCT as compared to an equivalent amount of LCT (7-10). This month we want to discuss a recent paper comparing the effects of MCT and LCT on energy expenditure in humans (11). Eight healthy young men were each fed four different diets on separate occasions and their metabolic responses were mea-sured in a respiratory chamber.
A respira-tory chamber is a special room where the atmosphere of the room can be monitored for the amounts of oxygen consumed and carbon dioxide produced by the person inside. From this information we can calculate total energy expenditure as well as the metabolism of carbohydrate and fat as fuel. Urinary nitrogen excretion is used to monitor protein metabolism. The men were fed four different diets all providing the same number of calories. Each diet contained a total of 30 grams (about two tablespoons) of a fat supplement. The diets differed in the ratio of MCT to LCT in the fat supplement. The ratios of MCT to LCT (grams to grams) in the four diets were as follows: zero to 30 (no MCT), five to 25, 15 to 15 (half MCT, half LCT), and 30 to zero (all MCT). During the study period the men were fed their baseline diets, which consisted of approximately 15 percent protein, 40 percent fat, and 45 percent carbohydrate. Each subject spent 24 hours in the respiratory chamber on four separate occasions, once for each of the fat supplements. During the stay in the chamber each man was fed his baseline diet plus 30 grams of one of the fat supplements at a total calorie intake designed to match maintenance energy requirements. In other words the subjects were fed at a calorie level intended to re-sult in weight maintenance and were not intentionally overfed or underfed.
The 30 gram fat supplement was fed in three 10 gram doses with each of three meals of the baseline diet. This amounts to about two teaspoons or 2/3 tablespoon of added oil per meal . It was found that 24 hour total energy expenditure differed substantially in diets containing 15 and 30 grams of MCT, with average increases of 38 and 113 calories per day respectively as compared to the diet providing only LCT. The diet provid-ing five grams of MCT supplement dur-ing the 24 hour period (about a teaspoon) did not show an effect. Thus there seems to be a dose-dependent increase in energy expenditure—diets providing more MCT result in higher metabolic rate. No differ-ence was seen in respiratory quotient or in nitrogen excretion, indicating that the overall balance between carbohydrate, fat, and protein metabolism was not af-fected—just the total energy expenditure. When fed the 30 gram MCT supplement, the subjects’ metabolic rates increased from between 64 to 180 calories per day, with an average increase of 113 calories per day. This was statistically significant (p < 0.001). This amounts to roughly a five percent increase in metabolic rate by switching from the LCT diet to the MCT-containing diet. We find this remarkable especially considering the small amount of MCT used in this study.
They used a total of 30 grams divided among three meals, which is about 2/3 of a tablespoon per meal. It should be noted that within the range studied, an increase in the amount of MCT resulted in an increase in metabolic rate. It seems reasonable that an even larger effect might be seen if larger amounts of MCT are employed. (Actually, this has been observed in other studies. One of the main purposes of this paper was to examine if diets containing small amounts of MCT would be effective in increasing metabolic rate.) We usually recommend people use between one and three tablespoons of MCT per meal to see a real effect, and most of our athletes eat more than three meals per day . This paper is important in demonstrating that a significant increase in metabolic rate can be achieved by incorporating as little as two tablespoons of MCT per day into the diet . So how does a diet containing MCT increase energy expenditure and meta-bolic rate? There are probably a couple of mechanisms at work. As we discussed earlier, conventional fats are preferen-tially routed for storage in adipose depots, a process which does not consume much energy . MCTs on the other hand are rap-idly metabolized and some of their energy is lost as heat during nutrient processing .
Another factor which may be responsible for the increase in metabolic rate seen with MCT feeding could be activation of the sympathetic nervous system (SNS). In the present study they observed an in-crease in 24 hour urinary norepinephrine excretion with increasing MCT to LCT ratio in the diet, suggesting possible acti-vation of the sympathetic nervous system by MCT (11). Interestingly, in rats fed MCT the increase in metabolic rate could by blocked by propanolol, a drug which blocks the SNS. The SNS is definitely involved in controlling metabolic rate and fat metabolism, and may in part be responsible for the increase in metabolic rate seen with MCT. Exactly how this effect is mediated is not clear, but it is known that SNS activity is stimulated by 3-hydroxybutyrate, one of the ketone bodies produced by MCT metabolism. At this point it is important to discuss the right way and the wrong way to use MCT. (Our concern here is with potential uses of MCT to affect changes in body composition. Last month we talked about how to use MCT to enhance endurance performance, which is a totally different topic.) If your goal is to gain weight, then it is as simple as adding CapTri® to your baseline diet. This will add extra calories to your diet and promote weight gain.
The beauty of CapTri® is that it has very little tendency to be stored as body fat, so you can increase calories and gain weight while minimizing fat accumulation. Keep in mind if you are in a calorie surplus and gaining weight that any conventional fat (LCT) you consume will be very prone to be stored as body fat. Any time you are gaining weight this means you are in a net positive energy balance—a calorie sur-plus. If any of those calories are supplied as long chain fats, then they will simply be stored as body fat. So to properly use CapTri® to promote weight gain, simply add it to your food to supply extra calo-ries, but be sure to minimize your intake of regular fat first and do your aerobics to burn off any excess fat. To use CapTri® to promote loss of body fat, it’s not as simple as just pouring some CapTri® onto your food. Some people have this misconception. There’s nothing magical about CapTri® that makes you burn more calories than you eat or any-thing like that. It’s that a higher propor-tion of the calories from CapTri® are lost as body heat as compared to other foods and therefore fewer calories are available to be retained as body weight. This results in greater reliance on stored body fat as a fuel source. So the idea is to replace a giv-en number of calories from conventional fat with an equivalent number of calories from CapTri®. For example, to achieve the results seen in this paper you would remove 30 grams of conventional fat from your diet and replace these with 30 grams of CapTri®.
CapTri® has a much higher thermogenic effect than regular fat and is much less prone to be stored as body fat, so by substituting CapTri® for regular fat this should increase energy expenditure and possibly over time reduce body fat levels. If you have already minimized your intake of conventional fat as much as possible, you could next try substitut-ing CapTri® for an equivalent amount of carbohydrate calories. This, theoretically, should further increase energy expendi-ture. This strategy would allow you to try the low carb approach without relying on conventional fat as the alternative fuel source. Many of our bodybuilders have used this approach with great results. CapTri® is very concentrated in calories, so you really need to weigh your food, count calories, and watch what you’re do-ing. But if you use it properly, you should achieve very good results. You might ask if you’re going to re-move 30 grams of conventional fat from your diet, why bother to replace it with 30 grams of CapTri®? Why not just cut out the calories? Won’t that work even better? Such an approach would result in faster overall weight loss, at least initially. However we have found that if people cut calories too much they end up losing muscle mass .
This ultimately results in de-creased metabolic rate and energy expen-diture. On low calorie diets your metabo-lism slows down and eventually weight loss grinds to a halt. By keeping energy intake up, this helps keep the metabolic rate from declining. The key is to provide the calories in a form which minimizes body fat accumulation. Of course, a small decrease in calorie intake is reasonable and can be very effective in promoting use of stored body fat as energy. The point is that you have to rely on something as your energy source, and we have found that many people can get a good result by minimizing conventional fats, consuming one to one-and-a-half grams of protein per pound of body weight per day, and then by meeting the remainder of their energy requirement by some combination of complex carbohydrates and CapTri®. The Parrillo Nutrition Manual goes into great detail in exactly how to do this and provides detailed information on how to adjust your diet to maximize muscle mass while minimizing body fat. You should also consult the BodyStat kit for impor-tant advice on how to change your diet to achieve your body composition goals.
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