High MCT Diets Are the Key to Longterm Fat Loss - True or False?

High MCT Diets Are the Key to Longterm Fat Loss - Yes or No?.

Eating tons of medium chain triglycerides (MCTs) will make you lean

Are we, or rather you, my American friend eating too much fat or simply the wrong type of fats? According to a study that was in the SuppVersity news in Nov. 2012, it's the latter the "SAD Diet Has the Optimal Ratio to Induce Diabesity" (learn more)
It depends. While it may be that you can derive certain benefits by kicking out junkfood from your diet and replacing it with MCTs the "fat-burning" effects of medium chain triglycerides (MCTs) wear off after one to two weeks (White. 1999). Unfortunately, this is way longer than the usually cited studies on the direct metabolic effects lasted, so that a cursory look at the research easily fools you to believe that you could effectively burn fat by simply using MCT oils instead of whatever "bad" fat you had been using before.

Moreover, in the aforementioned study that was published in the American Jorunal of Nutrition roughly 14 years ago the postprandial total energy expenditure was already only 3% higher after the MCT meal in the first week. And it's not only that this advantage disappeared within the next 7 days, the respiratory ratio, a measure of the ratio of carbohydrate to fat oxidation, total fatty acid oxidation and carbohydrate oxidation were also identical in the  32% MCT and 32% LCT diets (both diets contained additional 8% of fat from other sources).

But what about all the other research?

While the transient benefits of the MCT feeding on energy expenditure alone are unlikely to have practical relevance there are a good handful of trials, which show some real world benefits in various dieting scenarios. Unfortunately, they are usually too short (Alexandrou. 2007), compare MCTs to beef tallow & co only diets, observe increases in fatty oxidation, which don't translate into changes in body composition (St-Onge. 2003), or have the subjects in the control group use relatively fragile control oils, such as olive oil for frying and cooking (St-Onge. 2008).

Accordingly, you should not be too surprised that the latest review of the effects of dietary intake of medium chain triglycerides on body composition, energy expenditure and satiety concludes: "
Curried Carrot Soup w/ coconut oil certainly qualifies as a good food choice, also bc. it's made with coconut oil, not plain MCTs (more).
"In the present review it was possible to verify that data related to increased satiety after consumption of MCT are quite controversial. Most studies showed no significant difference as to increased satiety and/or satiation related to lipid consumption. [...] A relevant fact in the lack of consensus among the studies concerns the large variation in the amount of MCT provided in different studies due to lack of reference values for a minimum, ideal and maximum consumption in literature. Moreover, there isn’t enough to long-term studies to identify either beneficial effects or potential harmful effects." (Souza. 2013)
If you go through the list of studies included in the review there are a couple other interesting patterns emerging: (a) the effects - if there were any - originated from the gut (mostly greater satiety effects), (b) if there were effects on body composition those often reached statistical significance in the obese individuals, only, (c) the benefits were more pronounced the less the subjects ate (esp. on those 800kcal hunger diets), (d) when the control was not nasty corn oil, or saturated long chain triglycerides (Atkins diet style), the effects were non-existent.

So, if your are lean, your current diet is balanced and your main fat source is neither corn oil nor beef tallow, the chances that you will be better off with expensive MCT oils than with a couple of spoons of coconut oil in your diet probably border zero. You see, it's just as so often not so much about "adding something in", as it is about leaving something else out / replacing it with a better food choice.