Peter Attia revises his views as critic questions longevity

Peter Attia, one of the best-known figures in longevity medicine, has publicly walked back two pillars of his earlier approach to diet. A day later, another show offered a sharply critical portrait of him and the field he helped build.

On his own show, The Peter Attia Drive, Attia said he spent three years in strict ketosis, with morning beta-hydroxybutyrate (a ketone marker) averaging between 1.8 and 2.0 millimoles. He once believed that suppressing insulin was what drove fat loss and metabolic health.

He now argues that ketogenic diets work mainly through energy balance: cutting carbohydrates makes people feel full, so it is easier to eat less. Patients in a calorie surplus can still gain weight on keto, he said. He stopped the diet because of lifestyle restrictions, not health concerns.

That change has shaped his practice. Attia now says he is agnostic about diet structure, so long as patients eat enough protein, which he sets at a minimum of 1.4 grams per kilogram of body weight daily.

He also revisited fasting. For three years he did quarterly fasts of seven to ten days plus monthly three-day fasts, aiming to boost autophagy, the cellular recycling process that kicks in under nutrient deprivation. Preclinical data suggested about three days of fasting were needed for a significant rise.

But Attia said there is no reliable human biomarker for autophagy, so dosing is guesswork, while the muscle loss from long fasts was real. He pulled back. He framed this as "strong convictions, loosely held," a phrase he said he borrowed from a hedge fund manager, and said that giving identical advice a decade after his book would suggest either rigid thinking or no scientific progress.

"Strong convictions, loosely held."

- Peter Attia, The Peter Attia Drive

On Behind the Bastards, Dr. Kaveh Hoda took a harder line on the broader movement. He described longevity medicine as built on geroscience, the hypothesis that aging itself underlies chronic disease, and said its top tier leans on off-label rapamycin, metformin and NAD+, plus continuous glucose monitors for people without diabetes. Hoda said these practices lack rigorous human trials and often rest on mouse data or speculative biomarkers.

Hoda also argued the delivery model deepens inequality. A typical physician handles 2,000 to 3,000 patients, he said, while concierge doctors cut that to roughly 300, pulling clinical capacity out of the public system and making basic care a subscription for the wealthy.

He then traced Attia's origins: born in Toronto in 1973, trained in engineering and applied math, then Stanford Medical School. During his general surgery residency at Johns Hopkins, Hoda said, Attia built an Excel model overnight and changed an ICU patient's dosing of gentamicin, an antibiotic that can cause kidney damage and hearing loss, without approval from his attending or the pharmacy.

Reprimanded, Hoda said, Attia cast the clash as proof that traditional medicine stifles innovation. He left in his fifth year, telling Jocko Willink he resented the lack of meritocracy and uniform resident pay, and then joined McKinsey.

Hoda's wider worry is that tolerating small-scale wellness claims erodes scientific literacy and, eventually, trust in measures like vaccination. The two shows do not address each other, but they sit side by side: Attia presents his reversals as science working as intended, while Hoda questions whether the evidence ever supported the confidence.