The Peter Attia Drive - #411 ‒ AMA #90： Strong convictions, loosely held： how Peter's views on fasting, keto, metformin, rapamycin, whole-body MRI, and exercise have changed

00:00:00.000 Hey everyone, welcome to a sneak peek, ask me anything or AMA episode of the drive podcast.

00:00:15.820 I'm your host, Peter Atiyah. At the end of this short episode, I'll explain how you can access

00:00:20.280 the AMA episodes in full, along with a ton of other membership benefits we've created,

00:00:24.900 Or you can learn more now by going to peteratiyahmd.com forward slash subscribe.

00:00:30.580 So without further delay, here's today's sneak peek of the Ask Me Anything episode.

00:00:39.180 Welcome to Ask Me Anything episode number 90.

00:00:43.480 In today's AMA, we're reflecting back on the first 400 episodes of The Drive

00:00:49.680 with another episode of the Strong Convictions Loosely Held theme.

00:00:54.900 So what do we do with this? Well, we walk through some of the biggest positions I've taken

00:00:59.000 across the eight plus years of this podcast, but then we revisit them by basically asking,

00:01:05.580 where have the data taken us? What's changed, if anything? And as a result of that, of course,

00:01:10.240 where am I today? So in this episode, we're going to talk about my evolving views on ketogenic diets,

00:01:16.320 extended fasting as a longevity intervention, and the DRTRCR framework, why I stopped taking

00:01:23.220 metformin for longevity and my shifting position on rapamycin, whole body MRI and liquid biopsies

00:01:30.640 for cancer screening, including why I think whole body MRI data quality has actually gotten worse

00:01:36.280 over time and not better, how my approach to cardiorespiratory training and the 80-20 zone

00:01:42.980 two framework has changed, especially for people with limited training time, and why I stepped away

00:01:48.900 from heavy barbell squats and deadlifts and how to think about risk management in strength training.

00:01:54.840 If you're a subscriber and want to watch the full video of this podcast, you can find it on the

00:01:59.100 show notes page. And if you're not a subscriber, you can watch a sneak peek of the video on our

00:02:04.040 YouTube page. So without further delight, I hope you enjoy our celebration of 400 episodes together

00:02:09.540 with AMA number 90. Peter, welcome to another podcast. How are you doing? Very good. Thank you.

00:02:19.720 You? Doing good. Doing good. So today we are celebrating 400 episodes, about eight years.

00:02:26.240 So we recently crossed this. And usually what we do is every now and then we'll look back at kind

00:02:30.760 of a reflection episode. In the past, we've always referred to them as strong convictions,

00:02:35.340 loosely held. And so I think as we start, before we get into specific topics,

00:02:40.360 do you kind of want to remind people about what that term means to you, where you heard about it,

00:02:44.500 and why you think it's so important? Yeah, it's a term that I first heard from a friend who ran

00:02:50.700 a hedge fund. And obviously, this was through the lens of his investment thesis, which was that

00:02:55.840 obviously needed strong convictions, but because you're putting real capital behind the thesis.

00:03:00.120 but those convictions had to be loosely held because the moment new information or contradictory

00:03:05.640 information showed itself, you kind of had to be willing to check your ego at the door,

00:03:10.420 say maybe I was wrong and how do I need to change things? But I always thought that that frankly

00:03:14.680 was a great view of how to think about everything where there's actual information at play. And

00:03:21.480 obviously medicine and science are great examples of that. So I've been around many really, really

00:03:26.900 great scientists. And one of the characteristics they all have in common is they're not married

00:03:31.340 to a particular thesis being right. They're married to sort of getting things as right as

00:03:36.540 possible and reducing uncertainty by following the data wherever those data take them. So I think

00:03:43.120 it's important that we are revisiting our assumptions. And as someone asked me once,

00:03:50.340 you know, if you were to write Outlive 10 years from now, do you think it would be the same book

00:03:53.820 that you wrote, you know, three years ago. And I would say, no, I, in fact, that would be

00:03:58.940 concerning if it were the same book in 10 years as it was at the time it was written. Cause it

00:04:04.040 would either suggest I'm too rigid in my thinking or science has made no progress. And I think both

00:04:11.300 of those would be, would be challenging. So yeah, that's loosely how we think about this episode.

00:04:17.820 And Peter, when you're kind of looking at your opinions and how you're thinking about things

00:04:21.860 and how they evolved, where does that traditionally come from? What are the triggers that are causing

00:04:26.560 you to potentially change your opinion or how you look at things? I think it's a combination of

00:04:33.260 obviously things that change in the literature, but scientific progress is by its very nature

00:04:41.000 somewhat glacial and episodic. It doesn't just progress at the same rate. I think the other

00:04:47.660 sources of, of learning for me and things that forced me to change, maybe things I once held

00:04:53.680 would be the podcast itself, right? There's a opportunity I get most weeks to sit down with

00:04:59.600 someone who's far more of an expert in a subject matter than I am. And both in preparing for that

00:05:04.180 discussion, having a discussion, I'm learning something that often changes. I mean, almost

00:05:08.480 always changes something in how I think. And then obviously you have, uh, as every doctor hopefully

00:05:14.460 appreciates all of our patients are kind of our teachers, right? So we learn a lot because we're

00:05:20.800 seeing what happens in a clinic with patients. And we're, you know, we're going to talk about

00:05:26.640 some of these things today, frankly. So, you know, so basically I think all of these things

00:05:30.780 taken together, whether it be literature, conversations with experts and seeing what

00:05:35.540 actually happens in the clinic. I think a lot of times these things continue to converge

00:05:40.380 and the views don't change much. And other times the view just gets more nuanced and you start to

00:05:45.860 carve out edge cases and exceptions. And then sometimes it actually causes you to change course

00:05:51.140 completely. And obviously that's what I think this episode is all about and what makes this

00:05:55.720 type of episode for me personally quite enjoyable. I think as we start this, I think the topic that

00:06:01.340 makes the most sense to start at, which is everyone's favorite, nutrition. So kind of very

00:06:06.900 early on, way back in the day, you were a big proponent of the keto diet. You were also an

00:06:12.580 early adopter and advocate for kind of extended fasting and what that could potentially do

00:06:16.920 from a longevity perspective. And so kind of where are you now on those things and how has

00:06:23.660 your opinion changed? Well, my original thing, I'll start with the diet thing, was really driven

00:06:30.480 by this insulin model of obesity. So metabolic disease was and obviously remains kind of not

00:06:37.940 just one of the four horsemen of chronic disease, but kind of the foundational problem, right? So

00:06:43.160 it's the one thing where as metabolic health gets worse, your risk of all other chronic diseases

00:06:50.560 essentially goes up. And in my own journey of nutritional experimentation, carbohydrate

00:06:58.100 restriction was proving to be very beneficial. And as you stepwise move down the plank of

00:07:05.920 carbohydrate restriction, you're going to pretty quickly find yourself at a place which is generally

00:07:10.800 a line in the sand of ketogenic diets or not, right? Because at some point carbohydrate intake

00:07:14.760 gets so low that you're not providing enough glucose for your brain. But if it's still a

00:07:20.680 little high and it's too high to allow your body to switch over into ketosis, then you're not

00:07:26.800 getting enough supplemental energy for your brain and you're, you're in that kind of no man's land

00:07:30.940 of hell. And so I remember getting to that point and then deciding, well, you know, I, at that

00:07:35.600 point had been reading a lot about ketogenic diets and decided, look, I'm going to give this

00:07:38.220 thing a shot. So anyway, so that my own journey starts with my own experience, which was very

00:07:42.760 positive. I know I get sort of labeled as someone who's anti-keto diets and stuff like that by,

00:07:49.300 by various people out there. And I just find that to be the most comical critique of me because not

00:07:55.000 only was I on a ketogenic diet for three years, it was probably the best I ever felt. I look back

00:08:01.620 at what those three years were like, and every element of it was very positive for me. There

00:08:07.440 are other reasons, obviously, I chose to abandon it. Nevertheless, it reinforced the model in my

00:08:13.160 mind that the relationship between carbohydrates, insulin, hyperinsulinemia, lipogenesis, etc.,

00:08:21.060 was, you know, sort of, it all made sense that then a ketogenic diet would sort of fix these

00:08:25.440 problems. I think there were also lots of compelling data with, with animals and humans

00:08:30.380 showing the improvements in glycemic control, insulin sensitivity, liberal, liver, visceral

00:08:35.000 fat, et cetera, and other metabolic markers improving. And as I said, I certainly reinforced

00:08:40.340 that. Now here's what's different. I abandoned the ketogenic diet basically because I was just

00:08:48.440 tired of being that restrictive in my eating. I mean, I was very strict in my ketosis. I think,

00:08:54.560 you know, I also logged unprecedented amounts of data during this process. And I think over

00:08:59.600 a three-year period of time, you know, my average morning fasting beta-hydroxybutyrate level was,

00:09:06.860 you know, 1.8 to 2 millimoles, something in that range. So this wasn't, like, I wasn't sort of a

00:09:12.060 light ketosis guy. And then, of course, it would get much higher during the day, depending on what

00:09:16.580 I was eating because I was mostly eating fat. So my abandoning the ketogenic diet was independent

00:09:22.720 of my views of the ketogenic diet. And to this day, I still view it as an effective diet.

00:09:28.700 What has changed is my belief as to why it works. You see, I used to believe that the diet worked

00:09:36.620 through insulin suppression, but today I don't think that's the case. Today, I think the diet

00:09:44.360 works for the same reason many restrictive diets work, which is it makes it easier to control

00:09:51.720 energy intake, even if you don't have to think about it deliberately, which to be clear, I never

00:09:57.680 did, right? Now, of course, I wasn't losing much weight on a ketogenic diet because I'd already

00:10:01.200 lost most of the weight I was trying to lose just from carbohydrate restriction. But when I see

00:10:06.620 people who are successful on ketogenic diets, they often report that they feel quite satiated. And I

00:10:12.800 think that has to do with the type of foods that they're consuming, which satiate them more than

00:10:17.700 carbohydrates. And I also believe there's something to be said for when you are oxidizing fatty acids

00:10:24.540 that in and of itself is providing fuel endogenously, which is happening obviously during

00:10:29.360 a period of weight loss. So it's a subtle point, but it's worth making because it does reflect

00:10:35.740 a change in my viewpoint, which is that the metabolic dysfunction, the visceral fat accumulation,

00:10:44.320 the ectopic fat accumulation, the insulin sensitivity deteriorating, all of these things

00:10:49.320 are the result of the energy imbalance. And hyperinsulinemia is along for the ride.

00:10:55.880 But if you magically address the hyperinsulinemia without addressing the energy imbalance,

00:11:02.500 you're not going to fix these problems. And the easiest way to see that is to watch a person who's

00:11:07.440 on a ketogenic diet, who for whatever reason is still in energy imbalance. So they're still going

00:11:14.160 to have lower levels of insulin, but they're not going to lose weight and they could even gain

00:11:18.380 weight. So you could gain weight on a ketogenic diet if you're out of energy balance. So that's

00:11:23.100 sort of the long and short of my views on that. As a result, I think it's made me less, I mean,

00:11:28.880 much less dogmatic about the strategy or the tactics that a person employs when it comes to

00:11:35.500 reducing energy intake. I really don't have a strong preference when a patient is at a point

00:11:42.400 where they need to reduce intake. Once a few principles are met, and we've obviously talked

00:11:47.180 a lot about those things, right? I really am pretty adamant about people maintaining

00:11:50.600 the right amount of protein. And at a minimum, I want them hitting 1.4 grams per kilogram

00:11:56.060 of body weight. But if they can accomplish that on a ketogenic diet, on a low-fat diet,

00:12:01.640 on a mostly pescatarian diet, I mean, again, it just doesn't really matter as much to me

00:12:07.420 as it once did. So yeah, I think that's probably a big point around my previous dogmatism around

00:12:15.620 nutrition. And now looking at extended fasting, do you want to talk about kind of what was your

00:12:21.380 initial motivation there and where you're thinking as a bulb yeah i mean i think it's sort of similar

00:12:28.160 again a lot of things with me begin from a place internally right where i'm doing something and i'm

00:12:33.700 trying to push the boundaries of it personally so for about a three-year period of time i was doing

00:12:40.860 a quarterly fast and it would be anywhere from seven to ten days once a quarter and then on the

00:12:48.120 other two months of the quarter, I would do a three-day fast. And what was my logic for this?

00:12:53.940 I mean, to be clear, I was not trying to lose weight. I was at a weight that was perfectly

00:12:58.720 reasonable. But I was really fascinated by this idea that with enough nutrient deprivation,

00:13:05.700 we could promote enough autophagy that it would have real health benefits. And just to remind

00:13:11.560 folks. What autophagy is, autophagy is the process by which cells break down and recycle

00:13:18.420 old intracellular proteins and structures. So the name auto-self-phagy eating, it's literally

00:13:24.080 cells that are kind of eating themselves. And this is a very important process, obviously long,

00:13:29.820 long conserved in evolution, because when nutrients are scarce, the body has to basically

00:13:34.820 reuse and recycle things. Now, the benefit of this, of course, is that what is the body going

00:13:41.340 to do when it needs to reuse and recycle things? It's not going to start with the best stuff. It's

00:13:47.120 going to start with the worst stuff. So if you have cells that are heading towards senescence,

00:13:51.560 if you have cells that are developing mutations, the thinking goes, hey, that's where we're going

00:13:56.460 to start. Those are the cells we're going to get rid of and recycle for their constitutive

00:14:00.500 components. And again, in preclinical models, extended fasting clearly does this. So there's

00:14:07.180 little doubt that extended fasting promotes autophagy. As a little aside, Nick, and I haven't

00:14:13.140 looked at the literature on this in a couple of years, so maybe what I'm saying, someone will say,

00:14:16.880 no, Peter, we actually look at so-and-so study. But it wasn't really clear how many days of fasting

00:14:23.820 were necessary to get into quote high autophagy because autophagy is not digital it's analog it's

00:14:31.600 not like you have no autophagy and then you cross a threshold and now you have autophagy in a digital

00:14:37.700 switch it's it sort of ramps up kind of like ketosis now in ketosis we have a threshold we

00:14:43.360 use it's about somewhere between 0.5 and one millimole resting or fasting we don't even have

00:14:48.800 a unit of measure in autophagy to do that. But having spoken with the experts on this subject

00:14:55.680 matter and looking at preclinical data, somewhere around three days seemed to be where you could

00:15:02.800 really sort of juice autophagy levels beyond what you would get from exercise or other things like

00:15:07.960 that. Okay. So then the question becomes, well, why aren't you doing that still, Peter? And again,

00:15:14.980 And I think there were several reasons for that, but I think what changed most was kind

00:15:20.140 of the evidence, but also the cost.

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The Peter Attia Drive - October 12, 2026

#411 ‒ AMA #90： Strong convictions, loosely held： how Peter's views on fasting, keto, metformin, rapamycin, whole-body MRI, and exercise have changed

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