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Bulletin #36 – MCT’s – Setting The Record Straight

There has been some confusion in therecent bodybuilding literature about me-tabolism of medium chain fatty acids, ormore precisely, medium chain triglycer-ides. The specific areas of uncertaintyrevolve around whether MCTs are con-verted into ketones and if they are storedas body fat.Since what has been written containscome misinfomation, let’s start with thegeneral and move to the specific. First,when people disagree about technicalmatters like this it’s always nice to checktheir references. If somebody takes a po-sition and defends it by citing referencesto the scientific literature, he might beright or he might be wrong, but at leastyou have the option of checking the in-formation out for yourself to see if he hasinterpreted it correctly. When people com-ment on research results and don’t citeany references, then they’re asking youto take their word for it without furnish-ing any proof one way or the other. I tryto stay out of discussions like this becausewithout any objective data it just turns intoan argument about opinions. Don’t get mewrong: expert opinions are important andcount for a lot, but you can’t really havemuch of a discussion of scientific researchwithout citing the literature.The next general issue has to do withif MCTs are stored as body fat. Thisseemingly simple question has a relativelycomplex answer. Literally speaking, thehuman animal stores fat in the form oflong chain triglycerides, LCTs.

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These aretriglycerides comprised of fatty acids 14carbons long or longer.  Most fatty acidsin human fat are either 16 or 18 carbonslong, with a small percentage being longer.So, literally speaking, MCTs are not storedas fat in the human (or in rats, where a lotof research was also done). Does thismean we can eat all the MCTs we wantand never get fat? Of course not. If youeat too many calories you will gain weight,and for most people, most of the time,any extra weight they gain from over-eat-ing will be fat mass. I’ve said this beforemany times, but I’ll say it again to makesure I’m understood: too many caloriesfrom any source can be converted to fat.What you have to realize is that differentfoods are metabolized differently in thebody, and don’t all have the same tendencyto store as fat. So all foods have the po-tential to be converted into body fat ifconsumed in excess, and what bodybuild-ers want to do is pick the food choicesthat have the least tendency to do so, whilehaving the greatest tendency to contrib-ute to muscle tissue.So what is this business about differ-ent foods having different tendencies tobe converted to fat?

This is one of themost exciting and important discoveriesin nutrition since vitamins. It comes fromthe realization that while protein, carbo-hydrate, and fat can all be converted intousable energy in the form of ATP, theyfollow different metabolic pathways andare thus converted into energy with dif-ferent efficiencies. Chapter 8 in reference1 contains detailed calculations showingthat different dietary energy substrates areconverted into ATP with different yields.The experiments done specificallywith MCTs sought to determine if includ-ing MCTs in the diet can reduce fat accu-mulation during over-feeding, comparedto other foods. References 2-6 describewhat are the best studies done to date onthis issue. These studies are well-con-trolled trails in rats and humans that mea-sure the effect of replacing some part ofdietary energy as MCT. It was found thatif conventional fats (LCTs) are replacedby MCTs this results in diminution of fatstores. This is explained by the fact thatMCTs are profoundly thermogenic, so asignificant fraction of the dietary energysupplied by MCT is released as body heat,making it not available for storage as fat.References 2, 4, and 6 specially demon-strate the thermogenic effects of MCTs,including studies in humans.

Reference 7is an excellent review article on the sub-ject.Let me clear up one minor area ofconfusion on thermogenesis, while I’mon the subject. Thermogenesis, or moreproperly the thermic effect of feeding,refers to increases in body heat produc-tion following feeding.  All foods releaseheat when they are burned. Indeed, main-tenance of core temperature is one of themain functions of dietary energy. Differ-ent foods release different amounts of heatwhen they are burned. MCTs happen tobe profoundly thermogenic, meaning thatthey release a lot of heat (2,4,6,7). This isa consequence of the metabolic pathwaythey follow, which is in turn a conse-quence of their unique molecular struc-ture (7). It has nothing to do with increas-ing thyroid hormone or noradrenaline lev-els and re-setting the thermostat in thehypothalamus, but is merely a result ofrapid metabolism and conversion of di-etary energy to heat within the liver. Thisdoes not mean however that they increase body temperature. It has been well knownfor years that MCTs are thermogenic with-out increasing body temperature (7). Thisjust means that as more heat is produced,it is liberated to the environment. If foods,including MCTs, elevated body tempera-ture then we would get a fever after weate, and if we ate too much we would diefrom hyperthermia.

It doesn’t work thatway.Regarding the question of ketogen-esis, I’m glad that was brought up be-cause that’s one of the key things thatmakes MCTs so special. It is quite cor-rect that regular fats, including conven-tional dietary fats as well as body fat, arenot converted into ketones to any appre-ciable extent as long as carbohydrate fuelis available. This is because regular fatsrequire the carnitine shuttle to transportthem across the mitochondria membraneto the mitochondrial matrix, where theyare metabolized to produce ATP or elseconverted into ketones. The carnitineshuttle requires the activity of an enzymecalled carnitine acyl-transferase I, or CAT-I, which sticks a fatty acid onto carnitine,which then carries it across the mitochon-drial membrane. CAT-I is inhibited bymalonyl-CoA, a byproduct of carbohy-drate metabolism. This means that fatmetabolism is effectively shut down (orat least significantly down regulated) aslong as carbohydrate fuel is available, andthis is the molecular switch that does it.The special thing about MCTs is that theycan enter the mitochondria by passive dif-fusion, without the help of the carnitineshuttle (7). This means they are rapidlyoxidized as fuel even in the presence ofglucose (7). The MCT is burned so rap-idly, in fact, that the capacity of the Krebscycle to produce ATP (literally reducingequivalents, which are later converted toATP) is overwhelmed (7). This means thatMCT is burned faster than the mitochon-dria can produce ATP, so the rest of theenergy is converted into ketones.

Theketones then leave the liver cell and arecarried by the blood to muscle, where theyare used for energy (7). One of the mostamazing things about MCT is that it isconverted into ketones even in the pres-ence of glucose (7). This is a well estab-lished fact that has been in the literaturefor years. Many studies (reviewed in ref-erence 7) have shown a sharp increase inketone production following MCT inges-tion, even in the presence of glucose lev-els which inhibit ketone production fromregular fats.These ketones are taken up mostlyby muscle (the brain continues to run onglucose as long as it’s available) and rap-idly burned for energy. In fact, they areconverted into ATP preferentially over glu-cose, having what is called a “glucose-sparing” effect (7). The ketones areburned first, saving the glucose for later.If you don’t see ketones in your urine withKetosticks while you’re using MCT, thismeans it is working like it is supposed to,and the ketones are being used as fuel in-side muscle cells. If you use more andmore MCT, eventually you will indeed seeketones spilling over into your urine. Atthat point it means you’re using too muchand your supplement dollars are just end-ing up in the toilet.Now I want to get back to a questionI touched on earlier, and that is the issueof storage of MCTs as body fat. As I ex-plained, MCT is not directly stored as fat,but it is a concentrated source of calo-ries.

Too many calories in any form cancontribute to fat stores. How this happenswith MCTs is that they are broken downinto acetyl-CoA, which are two carbonfragments of fatty acids (acetate) attachedto co-enzyme A (Co-A). These acetyl-CoA units then can be re-assembled intolong chain fats, most commonly 16 car-bons long, and subsequently stored asbody fat (8). So while MCT is not storeddirectly as fat, it can be converted intoLCT which is stored as fat, just like anyother food. The point, which has beenproven over and over in the literature(2-8), is that calories derived from MCThave much less tendency to be con-verted into body fat than excess calo-ries from other food sources. This isbecause excess calories from MCT arepreferentially lost as heat through theprocess of thermogenesis, making themnot available for storage (2,4,6,7). Thismakes MCT the ultimate energy sourcefor bodybuilders, since it is a form ofcalories with less tendency to store asfat than conventional fats or even car-bohydrates.Finally, it deserves mention that noneof the scientific studies in the medicalliterature were done with bodybuilders.That’s where our research here atParrillo Performance picks up. We learnas much as we can from the literature,and then work on how to best use thatinformation to make better bodybuild-ers. We’ve personally done the researchover the years to determine the best wayto incorporate MCTs into a diet to de-rive maximum benefit from this uniqueenergy source.

If you’re still confusedand don’t know what to believe, youhave two options left. One is check outthe scientific literature for yourself. Bysiting specific references, I’ve givenyou that option. Second, try MCT foryourself and see if it works. Be sure touse it as instructed in the Parrillo Per-formance Nutrition Manual. The basicconcept is to substitute MCT-derivedcalories for an equivalent amount ofcalories from convention fat or carbo-hydrates. This increases the ther-mogenic effect of the meal, thus de-creasing fat storage. Some people makethe mistake of simply adding severalhundred calories a day of CapTri® to their normal diet without making anyother changes. This, of course, justadds calories to the diet and may in-crease fat accumulation and as men-tioned earlier, excess calories from yourdiet can be converted to body fat.CapTri® is not some magic fat-burn-ing chemical. CapTri® is not a drug.It’s just a very special nutrient that sup-plies energy in a way less likely to bestored as fat that regular foods.As with any supplement, the key isto use it in the proper way in combina-tion with the proper diet. There’s nosubstitute for a sound nutrition pro-gram, but by using supplements tocomplement your nutrition program,you can take your training and physiqueeven further. CapTri® is an extensionof the Nutrition Program. You use it foradded calories in your diet.

But youcan’t just start taking it, without firstestablishing a good nutrition program.So why use it? Here’s some of theways bodybuilders and other athletesutilize  this supplement in a positive way.First, CapTri® can help you gainmuscle, by providing extra energy forincreased intensity in workouts and bysparing amino acids that could be oxi-dized during this training. Second,CapTri® is used by bodybuilders as areplacement for carbohydrates whendieting. The key here is to change theinsulin:glucagon ratio so more fat isburned. By replacing carbs withCapTri®, you increase yourprotein:carbs ratio, thus decreasing theamount of insulin in the blood. Thatsparks the release of glucagon whichpromotes fat metabolism for energy inthe body. And while a low-carb dietalone would tired and lifeless, the calo-ries from CapTri® provide the energyto continue training hard and burningfat. Third, bodybuilder and enduranceathletes alike use CapTri® to increaseenergy for tremendous workouts. It’san additional energy source that can beused in the presence of carbohydratesto keep you going harder for a longerperiod of time.


1. Bjorntorp P, and Brodoff BN. Obe-sity. J.B. Lippincott Co., Philadelphia,1992.

2. Baba N, Bracco EF, and HashimSA. Enhanced thermogenesis and dimin-ished deposition of fat in response to over-feeding with diet containing medium chaintriglyceride. Am. J. Clin. Nutr. 35: 678-682, 1982.

3. Geliebter A, Torbay N, Bracco EF,Hashim SA, and Van Itallie TB. Overfeed-ing with medium chain triglyceride dietresults in diminished deposition of fat.Am. J. Clin. Nutr. 37: 1-4, 1983.

4. Hill JO, Peters JC, Yang D, SharpT, Kaler M, Abumrad N, and Greene HL.Thermogenesis in humans during over-feeding with medium chain triglycerides.Metab. 38: 641-648, 1989.

5. Lavau MM and Hashim SA. Effectof medium chain triglyceride on lipogen-esis and body fat in the rat. J. Nutr. 108:613-620, 1978.

6. Seaton TB, Welle SL, Warenko MK,and Campbell RG. Thermic effect of me-dium-chain and long-chain triglycerides inman. Am. J. Clin. Nutr. 44: 630-634,1986.

7. Bach AC and Babayan VK. Me-dium chain triglycerides: an update. Am.J. Clin. Nutr. 36: 950-962, 1982.

8. Hill JO, Peters JC, Swift LL, YangD, Sharp T, Abumrad N, and Greene HL.Changes in blood lipids during six days ofoverfeeding with medium or long chaintriglycerides. J. Lipid Res. 31: 407-416,1990.

2018-03-13T11:10:37-04:00 May 21st, 2009|Technical Supplement Bulletins|

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