Fats have gone through some unfortunate and unnecessary bad publicity over the years. Diet trends that discouraged fat intake overlooked many of the physiological measures our body takes to use these fats effectively. In some instances, even converting to a fat rich diet that can induce dietary ketosis has shown particular benefits for weight management, disease therapy and mental health.
Different fats can have a significantly different impact on how your body metabolizes those fats. That, in turn, has various consequences for how your body stores it, uses it, and extracts energy from it.
One such family of fats is known as medium chain triglycerides (MCTs) which have some remarkable properties.
What makes Medium Chain Triglycerides Different?
Dietary fats can be organized into three categories:
- Small Chain Triglycerides: 4 carbon atoms
- Medium Chain Triglycerides: 6-12 carbon chains
- Long Chain Triglycerides (LCTs): 14-20 carbon atoms
- Very-long Chain Triglycerides: 20+ carbon atoms
Most of the fats you’re likely to encounter in your diet (including: palmitic acid, stearic acid, oleic acid, palmitoleic acid, linoleic acid, alpha-linolenic acid, and others) are all long LCTs. Does that make them unhealthy? Not at all. In fact, the famed and beneficial Omega Fatty Acids are LCTs that have numerous applications for supplementing your diet and health. The difference comes down to how they are absorbed in the body.
LCTs must be broken down by bile salts and enzymes prior to being absorbed by your intestines. They are then reassembled into compounds that travel through the lymphatic system toward the heart where they are released into the bloodstream. From there they can then travel to necessary tissues such as the liver for energy production—though even this process is complicated and requires L-Carnitine to enter the mitochondria. This complex process is the path that the bulk of your dietary fat must take before being available for your body to use.
MCTs on the other hand go through a much simpler process via direct absorption into the blood once they reach the intestines. Not only does this give them a direct path to the liver for energy production but they are also capable of crossing the double membrane of the mitochondria on their own. This gives MCTs the benefit of providing fast energy without causing an insulin response.
MCTs can be broken down even further into the following forms:
- Caproic Acid (6 carbons—C6)
- Caprylic Acid (8 carbons—C8)
- Capric Acid (10 carbons—C10)
- Lauric Acid (12 carbons—C12)
Although caproic acid may have even better absorption than the others, it is also less available in foods making other MCTs like C8, C10, and C12 more accessible via diet and extracted oils.
Managing Weight & Metabolism with MCTS
The metabolism of MCTs in the body have been investigated on both animal and human models with results that seem to favour them over LCTs with respect to certain dietary and fitness goals.
There are multiple factors that can play into diet and weight loss. In a double-blind study, healthy men and women were put on a 12-week diet where fat intake remained the same, but was either targeted toward MCTs or LCTs and found greater loss in body fat and subcutaneous fat in subjects undergoing the MCT diet. 
Another study compared MCTs and LCTs in their role of energy expenditure and found that long-term consumption of MCTs enhanced energy expenditure and fat oxidation compared to LCTs.  Even appetite was affected as one study demonstrated when subjects ate significantly less food when consuming MCT when compared to LCTs before hand. 
Due to the difference in use in the body, LCTs are more likely to result in fat deposits that can influence metabolism. That MCTs are readily used by the body and not efficiently stored in fat deposits can be beneficial since they don’t give rise to metabolites that interfere with insulin signalling and promote inflammation. 
The Role of MCTs in Ketosis
Ketosis involves using ketone bodies in place of glucose for energy production in the body. While transitioning into a ketogenic state, the body must acclimate to switching its energy source from sugars to fats. Being able to supply your body with readily available ketone bodies may be beneficial for this process.
Caprylic acid (C8), for instance, can have a significant effect on ketone bodies in your system. An increase in 1mMol of plasma caprylic acid has shown to increase ketone body production by 5x.  Usually, if carbs are present, your body will default to using them for energy. However even with some carbohydrates present, C8 is still absorbed and utilized for energy.  This makes it a particularly useful tool for those looking to engage in a ketogenic diet by providing fast and readily available ketone bodies for energy. An added benefit is energy without insulin response which can be a big plus while transitioning or preparing for physical activity.
Medium chain triglycerides are available in dietary foods such as coconut oil, palm kernel, and various dairy products. MCT oil is also a concentrated option that is derived from some of the aforementioned dietary sources. Incorporating MCTs into your diet provides a great source of energy via quick and usable ketone bodies even in the presence of carbs making it great for those on a standard or keto diet alike.
- Tsuji , Kasai M, Takeuchi H, Nakamura M, Okazaki M, & Kondo K. (2001) Dietary medium-chain triacylglycerols suppress accumulation of body fat in a double-blind, controlled trial in healthy men and women. J Nutr.131(11):2853-9.
- St-Onge MP, Bourque C, Jones PJ, Ross R, Parsons WE. (2003) Medium- versus long-chain triglycerides for 27 days increases fat oxidation and energy expenditure without resulting in changes in body composition in overweight women. Int J Obes Relat Metab Disord. (1):95-102.
- St-Onge MP, Mayrsohn B2, O’Keeffe M, Kissileff HR, Choudhury AR, Laferrère B. (2014) Impact of medium and long chain triglycerides consumption on appetite and food intake in overweight men. Eur J Clin Nutr. 68(10):1134-40.
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