This is what I’ve had to say about Bulletproof coffee in the past: (keep in mind this was in response to someone in our graduate program, and that this would NOT apply for the duration of the 28-Days )
“I think the idea is that you drink this butter coffee instead of having breakfast – which will provide healthy fats and fill you up and give you energy.
My thinking is that a smoothie with protein and veggies and healthy carbs provides way more energy and nutrients than some butter and coffee. So I would never suggest that replacement.
As far as grass-fed butter as opposed to cream in coffee.. sure. Both are just a fat. Grass-fed is a better source of omega 3s so a better choice but most people are pretty sensitive when it comes to the consistency of their coffee and this change would not be significant enough for me to get people on it.
if you are in the habit of having a serving of fat with your coffee, this would be a neutral or marginally better substitution. If you aren’t, you would be adding calories to your day without much benefit that I can tell but if you aren’t trying to lose weight or if you are already having the fat, why not?”