We continue our discussion of coconut and coconut oil with a look at additional scientific facts about coconut oil. Tuesday's article revealed that coconut oil is not necessarily good for your heart, and in today's article, we shift focus to weight. Is coconut oil slimming? This article, by Dr. James J. Kenny, PhD, FACN, explores the data on the subject.
Dr. Mercola claims coconut oil will “…help stimulate your metabolism” and “…is the dieter’s best friend.” Dr. Oz announced on his TV show last year, "The first of the health benefits of coconuts - the one you're going care about a lot is weight loss."
Those who claim that coconut or coconut oil stimulates metabolism and aids weight loss base this claim not on studies done with either coconuts or coconut oil but rather MCT oil, which is distilled from coconut oil and palm kernel oils. However, MCT oil contains only two medium-chain fatty acids that make only a bit more than these oils. Back in the 1970s, when I fed animals MCT oil or corn oil, it was readily apparent that the animals fed the MCT oil gained significantly less weight. Research in human subjects has also shown that substituting MCT oil for longer chain fats and oils results in a short term increase in metabolic rate and increased satiety per calorie, leading to a reduction in body weight. So there seems to be pretty good data indicating that when it comes to weight control, MCT oil does appear to be slimming. However, just because MCT oil at the very least appears less likely to promote weight gain relative to longer chain fats does not prove than coconut oil -- in which over 85% of the fatty acids are longer than those found in MCT oil -- will have the same effect.
Perhaps Dr. Mercola and Dr. Oz and other who claim coconut oil is slimming might want to take a closer look at the data. Yes, MCT oil may very well have some unique properties, but it represents just about 10% of these oils. There are no well-designed clinical trials showing using coconut oil in place of other oils promotes weight loss. In the absence of controlled clinical trials, the best data we have may be the people eating lots of coconut on the Pukapuka atolls and even more coconut on Tokelau Island. Back in the 1970s the Pukapukans got 34% of their calories from coconuts and coconut oil and the Tokelauans a remarkable 63% of their calories came from coconuts. Both groups ate very little sugar, with most of their calories other than coconut coming from starchy plants and fish. The Tokelauans got just 3% of their calories from sugar, 18% from taro and breadfruits and 13% from fish and meat. A low carb diet to be sure! The Tokelauan middle-aged 35-54 who were consuming the majority of their calories each day from "slimming" coconuts back in the 1970s had an average BMI over 30. They were considerably heavier than the Pukapuans whose BMIs were closer to that of Americans.
Bottom Line: The claim that coconut or coconut oil speeds up the metabolic rate and promotes weight loss appears to be based solely on research done with MCT oil. Coconut oil appears to have very different effects on body weight than the MCT oil extracted from it. Despite all the claims about coconut oil or coconuts being slimming, there still are no credible clinical trials to support such claims. Making unsubstantiated health claims is the essence.
By James J. Kenney, PhD, FACN
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