Butter contains high levels of fat , which is what makes it so tasty. When your body is introduced to fat, ghrelin (aka "the hunger hormone") is suppressed, says Tracy Lockwood Beckerman , MS, RD, a registered dietitian in New York City. In theory, if you drink a cup of Bulletproof coffee first thing in the morning, you're less likely to experience normal mid-morning hunger pangs. To be clear, confusing your body into thinking you're satisfied is not really something to aim for, because it flips the intuitive eating concept — that you should honor your hunger cues — on its head. (Also, like, we need to crave and eat food to survive.) Nevertheless, hunger-suppression is a big selling point for people who are into the Bulletproof life.