New Bulletproof Fasting Method Burns 66% More Fat

Summary

Dave Asprey presents a version of fasting he calls “Bulletproof” fasting: coffee blended with grass-fed butter and C8 MCT oil. He says the added fat can provide energy and ketones while keeping insulin low, making fasting easier and supporting fat loss, focus, and muscle retention. These are his claims; he also notes that some of the research he discusses did not test the exact coffee recipe.

He contrasts his approach with 16:8 fasting, citing a 12-week study of 116 people in which, he says, 65% of the weight lost was lean mass. He acknowledges that the study was one experiment and that the difference in total weight loss versus usual eating was not statistically significant.

Method and practical tips

• Basic recipe: Blend one cup of coffee with 1 teaspoon of C8 MCT oil and 1 tablespoon of grass-fed butter for at least 20 seconds. He recommends blending rather than stirring so the fats emulsify.
• Increase gradually: Start with a small amount of MCT oil to reduce the chance of digestive upset. He suggests working up over about two weeks to roughly 1 tablespoon of C8 and 2 tablespoons of butter.
• Use it in the morning on an empty stomach: Asprey says this is the best timing for helping curb hunger through the morning.
• Choose C8 specifically: He distinguishes C8 MCT oil from coconut oil and generic MCT products, saying they may not produce the same ketone response.
• Keep the fasting window free of protein and carbohydrates: His approach avoids milk, cream, protein powder, and sweeteners during the fasting period. He argues that calories from fat do not end the kind of fast he is advocating, while protein and carbohydrates do.
• Eat in response to hunger rather than the clock: He suggests waiting until genuinely hungry to eat and says to break the fast with at least 30 grams of protein.
• Choose coffee carefully: Asprey attributes cravings and energy dips partly to mold toxins in some coffee and recommends coffee tested for them. This is his explanation and product recommendation.

Rationale and research claims

• Asprey says C8 is rapidly converted into ketones, which can serve as an alternative fuel for the brain. He argues this may help reduce hunger and the body’s reliance on muscle protein for glucose.
• He cites a small study of 19 overweight men comparing medium-chain fats with longer-chain fats. He reports greater weight loss during the MCT period and presents this as the basis for the title’s “66% more fat” claim.
• He also discusses research on ketones and hunger hormones, inflammation, and BDNF, a growth factor associated with the brain. He notes that some of this evidence comes from ketone drinks, cells, or animal studies—not from the exact butter-coffee routine in humans.
• He attributes other proposed benefits to fasting and ketones, including autophagy, reduced inflammation, and support for mental sharpness. These are presented as his interpretation of the research, not as established results of this specific recipe.

Presenters and sources mentioned

• Presenter: Dave Asprey
• Sources and research referenced: A randomized 16:8 fasting study of 116 people published in JAMA; the Rotterdam Study; a study comparing medium-chain and long-chain fats; a 2017 study comparing C8 with coconut oil; a 2018 study on ketones and ghrelin; a 2015 Nature Medicine paper on ketones and the NLRP3 inflammasome; 2016 research on ketones and BDNF; and the 2016 Nobel Prize in Medicine for work on autophagy.