I think the most charitable reading of their comment would be something like "replace other fats you use (butter, olive oil, etc) with coconut oil for two weeks".

Edit: you added your edit while I was writing my comment :)

MCT oil made from coconuts.

You can mix it in with things like coffee and shakes, easy way to get it.

>Coconut oil is the least fattening of all the oils. Pig farmers tried to use it to fatten their animals, but when it was added to the animal feed, coconut oil made the pigs lean [See Encycl. Brit. Book of the Year, 1946].

https://raypeat.com/articles/articles/unsaturated-oils.shtml

IIRC, that was more from the fact that coconut oil has zero linolenic acid, which is an essential metabolite. Coconut oil is still a huge calorie source for livestock, just that it's also mixed with soybean oil.

Basically, any combination of coconut oil in your diet that isn't 100% coconut oil will lead to calorie gain.

I would hope that there would be a better source than a 75 year old "summary of news book". If this is true there would surely be more recent and thorough scientific studies.