In general, Asprey’s recommendations are characterized by cherry picking, a tendency to cite studies that don’t really claim what he thinks they claim (or that they suggests, as when he conveniently fails to mention that the studies are performed on mice but not humans), or that he mischaracterizes partially because he doesn’t know enough about the rest of the field nutrition to determine the significance of the findings – Asprey has no credentials in any field relevant to the issues he talks about.
His fans are more impressed than the experts, given that the scientific establishment must be corrupt since they, who have no financial stakes in the issues, are critical of the advice of Asprey, who does. So it goes. He’s got plenty of celebrity endorsements as well. In fairness, many of his recommendations are unlikely to harm and may even help (though not necessarily for the reason he gives), though some are ridiculous rubbish, such as his opposition to sucralose and his endorsement of raw milk.
The bulletproof diet’s trademark selling point, however, is promotion of consuming large amounts of stimulants, specifically caffeine and the prescription drug Modafinil. Indeed, Asprey recommends replacing breakfast with substantial amounts of “Bulletproof Upgraded Coffee” (mixed with a spoonful of “Bulletproof Upgraded MCT Oil” and fat – his diet tends to forego proteins in favor of fat) because it is purportedly low in fungal toxins, something Asprey falsely claims is bad for cognitive performance. He also claims that most people are “[s]uffering from a Modafinil Deficiency”, which is false and gels poorly with his general appeal to cavemen given that Modanifil is a synthetic drug. Asprey claims to have been on a 300mg daily dose of the stimulant for more or less a decade, together with synthetic hormones (“testosterone replacement therapy”). He also suggests injecting your own urine into yourself to relieve allergy symptoms. Which is, hopefully needless to say, not a very good idea. Science writer Julia Beluz characterized Asprey’s bullshit aptly: “The Bulletproof Diet is like a caricature of a bad fad-diet book. If you took everything that’s wrong with eating in America, put it in a Vitamix, and shaped the result into a book, you’d get the Bulletproof Diet.” There are other, reasonable critiques of his bullshit here, here and here.
Asprey managed to throw himself into the limelight again in 2020 when he decided to “hack coronavirus” (“biohacking” remains his favorite term) and endorsed a long list of products that aren’t going to help you, including andrographis, probiotics, vitamins, coenzyme Q10, omega fatty acids, black cumin seed oil, hydroxytyrosol, sulforaphane and l-glutamine, and directed readers to his own products for sale. The fun lasted until The Federal Trade Commission asked him to stop because he could provide no evidence for the efficacy or safety of his advice.
Diagnosis: Yes, he is indeed everything that is wrong with America rolled up into one, perhaps apart from fundie wingnuttery. His products do not work, his advice is shit, and he is, for all practical purposes, a conman, even though he probably does believe his own claims.
Hat-tip: Rationalwiki, Julia Beluz