Can MCTs Help You Lose Weight? Yes, They Can! Latest Meta-Analysis Says MCTs 'Safe, But Not Super Effective'

Yes, coconut oil does contain MCTs, but it is not as some people believe pure MCT. Only ~50% of the fat in coconut oil is actually in MCT form. If you want pure MCTs you have to resort to specific MCT supplements / oils.

The mechanisms by which medium-chain triglycerides (MCTs) may help you to lose fat are manifold. They are not only hard to store for your body. They also counteract fat deposition in adipocytes by increasing thermogenesis and satiety.

MCTs contain 8 to 12 carbon atoms and include caprylic acid (C8:0, octanoic acid), capric acid (C10:0, decanoic acid), and lauric acid (C12:0, dodecanoic acid). Foods high in MCTs include coconut oil (58%), palm kernel oil (54%), desiccated coconut (37%), and raw coconut meat (19% of total energy) (USDA). Average intakes of 1.35 g/day (0.7% of total energy intake | USDA. 2008) MCTs have been reported in the United States and 0.2 g/day in Japan | Kasai. 2003).
MCT is cleaved into glycerol and medium-chain fatty acids in the gut lumen.5 The medium chain length makes a smaller, more soluble molecule compared with a longchain fatty acid, giving it a preferential absorption and metabolic route in the body. As the authors of the latest meta-analysis of the effects of MCTs on body weight say:

"[t]his physicochemical nature of medium-chain fatty acids allows them to pass into the portal vein on route to the liver to be rapidly metabolized via b oxidation with no requirement of reesterification in intestinal cells, incorporation into chylomicrons, or the rate limiting enzyme carnitine acyltransferase for intramitochondrial transport. In comparison, long-chain fatty acids have a slower route, being re-esterified in the small intestine and transported by chylomicrons via the lymphatic and vascular system before being oxidized for energy or stored. Thus, rapid metabolism of MCTs reduces their opportunity of adipose tissue uptake." (Mumme. 2015)

Several human intervention studies have been conducted investigating the weight-reducing potential of MCT, with mixed results. In their latest meta-analysis, Mumme et al. set out to separate the wheat from the chaff in order to answer the question whether MCTs, specifically C8:0 and C10:0, provide significant weight loss benefits and/or trigger changes in body composition compared to "regular" long-chain fatty acids (LCT).

Figure 1: Meta-analysis for changes in body weight (in kilograms) in randomized control trials that compared dietary medium-chain triglycerides (MCTs) with a longer-chain triglyceride (control) shows a favorable effect of MCT intervention on body weight. *Oleic acid as control. **Myristic acid as control. #Body mass index < 23. ##Body mass index > 23. IV inverse variance. SD standard deviation (Mumme. 2015).

The researchers' primary outcome measures were body mass, waist and hip circumference, total body fat, and subcutaneous and visceral fat. Secondary outcomes were blood lipids, including triglycerides (TG), total cholesterol, high-density lipoprotein (HDL) cholesterol, and LDL cholesterol. Of the latter the foremost values are those that are of greatest interest and among them the body mass shows a measurable, albeit not earth-shattering reduction in almost all trials. Only the in the 2001 study by Matsuo et al. there was an increase in body weight in response to an MCT supplement that contained almost no medium chain triglycerides.

Figure 2: Meta-analysis for changes in total body fat, total subcutaneous fat, and visceral fat (Mumme. 2015).

In view of the fact that the most relevant obesity parameters, i.e. the waist and hip circumferences and body fat percentages (Figure 2) dropped in all studies that investigated this parameter and considering the fact that there were no significant deterioration - rather improvements - in blood lipids, it appears warranted to assume that the replacement (!), but not the addition, of 2g/day MCTs (1% of the energy) to 54 g/day MCTs (20% of the total energy intake)  over a duration of 4 to 16 weeks leads to measurable and potentially health relevant weight loss, compared to bacon, butter & co, i.e. regular long chain fatty acids.
References:

• DeLany, James P., et al. "Differential oxidation of individual dietary fatty acids in humans." The American journal of clinical nutrition 72.4 (2000): 905-911.
• Hamman, Richard F., et al. "Effect of weight loss with lifestyle intervention on risk of diabetes." Diabetes care 29.9 (2006): 2102-2107.
• Kasai, Michio, et al. "Effect of dietary medium-and long-chain triacylglycerols (MLCT) on accumulation of body fat in healthy humans." Asia Pacific journal of clinical nutrition 12.2 (2003): 151-160.
• Mumme et al. "Effects of Medium-Chain Triglycerides on Weight Loss and Body Composition: A Meta-Analysis of Randomized Controlled Trials." EAT RIGHT - Research Review (2015).
• US Department of Agriculture. Nutrient Intakes From Food: Mean Amounts Counsumed per Individual, One Day, 2005-2006. Washington, DC: US Department of Agriculture, Agricultural Research Service; 2008.