Medium-chain triglycerides – Ultimate weight loss supplement for 2021?

Medium-chain triglycerides or MCTs are neutral lipids which contain fatty acid molecules with a chain length varying from 6 to 12 carbon atoms [1]. They were first introduced in 1950 for the treatment of disorders of lipid absorption. MCT oil occurs naturally in coconut oil and other foods and are consisted of caprylic and capric fatty acids. MCTs are used for various purposes (with or without medications): food absorption disorders, celiac disease, liver disease, and digestion problems [23]. Lately, MCTs have became very popular supplement for athletes who use them as nutrition support during as well as for decreasing body fat and increasing lean muscle mass.

Natural Sources of Medium-chain Triglycerides

Some of the rich sources of MCTs are [2]:

Coconut oil: 15%
Palm kernel oil: 7.9%
Cheese: 7.3%
Butter: 6.8%
Milk: 6.9%
Yogurt: 6.6%

What is the appropriate dose of MCT oil?

MCT oil supplementation in clinical studies typically varies between 5 to 50 grams [2]. If you assume 5 grams should be enough for you than you can go for coconut oil, while in order to reach upper end you will have to go with supplemental MCT oil.

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Metabolic effects of MCTs

The molecular weight of MCTs is smaller than the molecular size of long-chain triglycerides (LCTs) thus MCTs are hydrolyzed faster and more completely. The products of MCTs hydrolysis are absorbed very fast (as fast as glucose) [3]. This is due to the fact that MCTs cross the double mitochondrial membrane very rapidly, and do not require the presence of carnitine, as do LCTs [4]. This causes energy-enhancing properties. Additionally, MCTs (while still densely caloric) provide about ten percent fewer calories than LCTs (8.3 calories per gram for MCTs vs 9 calories per gram for LCTs) [2]. This accelerated metabolism does not mean that consuming them will cause weight gain, instead the calories contained in MCTs are (as mentioned before) very efficiently converted into fuel for immediate use by organs and muscles [5].

Weight Loss Evidence

Studies in rodents reported that MCTs decrease fat deposition through the enhancement of thermogenesis [6,7]. Same was noted in clinical studies [2,8-11] as fat oxidation and energy expenditure were also greater after consumption of MCTs compared to consumption of LCTs in both normal and obese subjects.

For example, Hiroaki, et al. [2] showed that subjects who consumed MCT oil over 12 weeks period lost 2 pounds more than control group. 48g of MCT resulted in a greater rise in oxygen consumption after a meal from the basal level than did LCT consumption in healthy men [12]. Even low-dose of MTCs has beneficial effect. For example, up to 10 g of MCT increases diet-induced thermogenesis further than LCT in healthy humans [13]. Furthermore, Tsuji et al. [14] reported that consumption of MCT at 10 g/day
for 12 weeks reduced body weight and fat in obese subjects.

MCTs have also shown promise for appetite control as they may suppress appetite. In a 14 day trial [15], energy intakes were significantly lower in volunteers on the high MCT diet compared to medium and low MCT diets.

MCTs and Exercise

Studies in animals reported that combination of a diet containing MCT and exercise have additive effect on the reduction of body fat accumulation [16]. A 2 week study [17] in recreational athletes who were ingesting food containing small amounts (6 g) of MCT during moderate-intensity exercise and high-intensity exercise, reported reduced blood lactate concentration and increased exercise intensity during moderate-intensity exercise and extended duration of subsequent high-intensity exercise compared to LCT. During repeated 2 hour cycling rides, MCT oxidation has been shown to directly and/or indirectly (via lactate) decrease oxidation of muscle glycogen [18]. Thus, an increase in fat utilization capacity is associated with resistance to fatigue [19]. It is not surprising that well-trained athletes have increased fat utilization capacity [20].

MCT Side Effects

MCTs are essentially non-toxic in acute and long-term toxicity tests conducted in several species of animals. At doses up to 4.28 g/kg body weight/day (intravenous) or 12,500 mg/kg body weight/day (oral) no evidence of adverse effects have been reported in animals. The safety of human dietary consumption of MCTs, up to levels of 1 g/kg, has been confirmed in several clinical trials. [21] Also, adverse pregnancy outcome from exposure to MCT appears unlikely [22].