#411 ‒ AMA #90: Strong convictions, loosely held: how Peter's views on fasting, keto, metformin, rapamycin, whole-body MRI, and exercise have changed
October 12, 2026
AI Summary
5 min readOver eight years and 400 episodes of The Drive, Peter Attia has held strong positions on nutrition, fasting, supplements, screening, and exercise. In this AMA, he revisits those positions through the lens of “strong convictions, loosely held”—a principle borrowed from a hedge fund friend that demands willingness to change course when data or experience contradicts a thesis. Attia walks through where the evidence, clinical experience, and his own physiology have led him to revise, refine, or abandon earlier views. The result is a candid look at how scientific humility plays out in real time across several major domains of longevity medicine.
Why the Keto Diet Works (and Why Attia Stopped Doing It)
Attia was an early and vocal proponent of the ketogenic diet, having followed it strictly for three years. His morning beta-hydroxybutyrate levels averaged 1.8–2.0 mmol—well into deep ketosis—and he felt better than he ever had. His original belief was that the diet worked primarily through insulin suppression, consistent with the insulin model of obesity. But he has since changed his mind.
Continue reading the full summary in the app — free to try.
Read Full Summary →Free • No credit card required
Never miss an episode of The Peter Attia Drive
Get every new episode summarized in your inbox — free, ~5 minutes to read.
No spam. Unsubscribe anytime.
What you'll learn
- 1 (00:10) **Introduction to the “Strong Convictions, Loosely Held” Framework** - Peter explains the purpose of the episode: revisiting major positions he’s taken over 400 episodes and eight years of the podcast.
- 2 (06:05) **Nutrition: From Keto Dogmatism to Flexibility** - Peter traces his journey from a strict ketogenic diet to a more pragmatic view focused on energy balance.
- 3 (12:26) **Extended Fasting: Revisiting Autophagy and the Cost-Benefit** - Peter explains his former practice of quarterly 7-10 day fasts and why he no longer does them.
- 4 (15:14) **[Sneak Peek Ends] Premium Membership Details** - Peter outlines the benefits of becoming a premium member to access the full AMA episode.
+ Full timestamped outline available in the app
Guests on this episode
Show Notes
View the Show Notes Page for This Episode
Become a Member to Receive Exclusive Content
Sign Up to Receive Peter's Weekly Newsletter
In this "Ask Me Anything" (AMA) episode, Peter looks back on 400 episodes of The Drive with another installment of "strong convictions, loosely held," revisiting some of the positions he has taken over more than eight years of the podcast. He explains why changing one's mind in response to new evidence, conversations with experts, and clinical experience is essential for practicing medicine well. Peter begins with nutrition, describing how his views on ketogenic diets, extended fasting, and the framework of dietary restriction, time restriction, and calorie restriction have evolved. He explains why he no longer takes metformin for longevity and discusses his growing uncertainty around rapamycin despite compelling animal data. Peter also revisits his views on cancer screening, including whole-body MRI and liquid biopsies for early detection. On exercise, Peter explains how his approach to cardiorespiratory training and the 80/20 Zone 2 framework has changed, particularly for people with limited time to train. He also shares why he has moved away from heavy barbell squats and deadlifts and how he now thinks about balancing benefit and injury risk. Throughout the episode, Peter emphasizes the importance of focusing on durable principles, strong foundations, and sustainable practices rather than chasing optimizations that provide marginal gains.
If you're not a subscriber and are listening on a podcast player, you'll only be able to hear a preview of the AMA. If you're a subscriber, you can now listen to this full episode on your private RSS feed or our website at the AMA #90 show notes page. If you are not a subscriber, you can learn more about the subscriber benefits here.
We discuss:
- Strong convictions, loosely held: changing opinions as evidence, expert conversations, and clinical experie
More from this podcast
The Peter Attia Drive →