I think a lot of people are confused about the purpose and the effects of the BP intermittent fasting, but he goes into detail about it at The Bulletproof Executive - the original website for it.
Basically, it primes your "mTOR" mechanisms; the coffee kicks up your metabolism, the butter gives you energy, and the MCT oil kicks up your metabolism. The purpose of BP IF *IS* fat loss. It has helped me break my fat-loss plateau in under a week. So for those worried about gaining weight on it, it's nearly impossible if you're eating right.
Also, the MCT oil is important... coconut oil is 50%MCT. This is pure MCT. The purpose of using this, no heavy cream, no sugar, is so that you can PRIME your fat burning! It also gives you a nice mental kick.
So, follow the bulletproof recipe exactly for the most prime results:
2 TBS butter
2 TBS MCT oil
That is all.