So I know there has been a lot of talk about coffee and intermittent fasting, and the fact that black coffee doesn't interrupt a fast. I do the leangains approach and enjoy my cup of joe in the morning. However, recently, I have been doing a bulletproof coffee (http://www.bulletproofexec.com/how-to-make-your-coffee-bulletproof-and-your-morning-too/) which is essentially coffee with a good amount of grass fed butter melted/blended in. I also take a vitamin k2/d3 supplement at this time since I figure I am getting quite a bit of fat so it is a good time to take fat soluble vitamins. I actually enjoy the taste of the bulletproof coffee and it gives me good energy. I feel like my "fast" can last longer and I don't really get hungry until well into the afternoon.
However, I am wondering if by adding butter to my coffee, I am ruining the effects of the fast... and if it is actually a "fast" anymore, since I am taking in a few hundred calories of fat. I emailed Martin Berkhan (leangains) and he said: "if you want to lose fat, dont put some fucking oil or butter in your coffee, it's bullshit."
He didn't really provide any actual scientific reasoning though so I was left unsatisfied. I figured I would ask you guys. How would adding grass fed butter to my coffee affect the intermittent fast?