Bulletproof Coffee was invented by self-described bio-hacker Dave Asprey. He uses mold-free coffee blended with unsalted butter and MCT oil. I've had it and it is very tasty. I don't know if it is the wonder beverage that Asprey says it is, and his claim that a lot of coffee has harmful mold in it is dubious. (Watch this video on the Joe Rogan podcast where Rogan talks about sending different coffee samples to testing labs and learning than none of them have mold).
Recently, Matthew Perger, a world champion barista, roaster, green buyer, consultant and partner at St Ali and Sensory Lab in Melbourne, Australia got to the bottom of Bulletproof Coffee in a fascinating blog post.
Will I lose weight by drinking it? That sounds easy! Give me a Bulletproof coffee please!
Short Answer: No.
Long Answer: Bulletproof coffee is like a really fatty latte. And when I say fatty, I'm talking somewhere close to your entire recommended daily intake of fat (~60g per serving). This isn't necessarily a bad thing. Many popular studies have recently salvaged fat's reputation as diet devil, showing that fats can be part of balanced diets. But, 440 calories is 440 calories. If you eat it, your body will burn it or store it somehow.
Most humans that would potentially drink a bulletproof coffee spend a lot of the day in an anabolic state. That is, they're well fed, and blood glucose is relatively high from eating. This means their body is content to store any excess calories as glycogen in the muscles and liver, or fat in adipose tissue. If you consume fat in an anabolic state, it's more than likely to be stored as fat, because that's easiest for the body. But Bulletproof coffee has a trick up its sleeve.