Fast This Way: World-Renowned Biohacker’s Fasting Strategies with Dave Asprey

The easiest thing you can do is have dinner a little bit earlier, because if you had, say, finished dinner at 6 and then you don't eat dessert, it goes from 6 till 10, that's 4 hours. You sleep for 8 hours, maybe that's 12 hours, and you wake up at 6 AM. If you have breakfast at 10, you just did a 16-hour fast, but to your mind, you really just kind of had breakfast a little bit late. It's pretty darn manageable.

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Our mission is to decode the neurobiology of flow and cognitive peak performance. Access the minds of maverick scientists, groundbreaking innovators, and world-leading experts to understand what it takes to achieve ultimate human performance so you can feel your best, perform your best, and accomplish your boldest goals. I'm your host, Ryan Dorris, and together with bestselling author Steven Kotler, I present to you Flow Research Collective Radio. Dave Asprey, welcome to Flow Research Collective Radio. It is great to have you here. So your new book, Fast This Way, has been popping up all over the place, and I'm curious just to kick us off, why a full book on fasting? Why does it merit a full book?

I spent years studying all of the different aspects of diet and nutrition that would work to make brains work better, and I put it all in my first big book called The Bulletproof Diet, and it included intermittent fasting. And in the past 10 years, people have lost a million pounds using intermittent fasting. Plus, it included things like lectins and plant toxins and cyclical keto, but not regular keto— all the stuff that's now coming out here. But since that time, I've seen keto devolve into a, if it's not a carb, you can eat it, and it doesn't work and it breaks people. And I've seen So many mistakes that people make from trying to oversimplify. And I realized what's the one thing that people have the biggest aversion to that has the highest return on investment of anything you can do for your health when it comes to food? And it turns out it's skipping breakfast. Because if you think about it, it's like you go to the bank and then they give you money when you walk in the door. That's because you didn't have to buy breakfast. No money, no time, no energy on breakfast. And then like, oh, here's some interest. You're like, but I didn't make a deposit. That's okay. 'cause you got more energy that morning from fasting than if you had breakfast. And then over time, you don't get type 2 diabetes, cancer, heart disease, all the other bad stuff. So you're like, wait a minute, I got long-term interest, short-term interest, and I got given money instead of having to put money in. It's like a negative investment in a bank. So why don't people do it? That's why I wrote the book, so that we could figure out how to do this for 10 years, 'cause I have enough experience with enough people. And also the spiritual side of fasting is really important. And I fasted in a cave for 4 days around that. So partly is don't try to do a spiritual fast during a workday. And here's how to make fasting easy and not painful. And if we could get people to do that, this would change so many people's lives. That's why I wrote it, even though frankly, it's the worst book you could write in terms of topics, just because who wants to talk about not eating breakfast?

Can I ask you a question about what you just said? Because I understand why you're saying it, but the energy back into the system, that's once you get used to living this way, right? Because in the beginning, it's a distraction and it's taking energy out of the system.

Only if you don't hack it. That's okay. In a normal fast, way back in the day before we had technology, you would say, oh, if I'm used to eating carbs— which humans generally weren't that used to eating carbs except in the middle of summer— but we would say, this is a problem, I'm going to feel like crap for 2 days. And then after the 3rd day, when your body kicked into ketosis, you would suddenly not care about food and you'd have tons of energy. My supposition, having lost that 100 pounds and all of my own health problems, is that most people who are trying to hold down a job— now they have kids jumping up and down on them while they're trying to hold down a job at home. We have plenty of stress. And to tell someone who's as fat as I was, oh, by the way, you're just not going to have breakfast— they're going to get hypoglycemic the way I would have. They're going to not be able to do it, and it's going to be a terrible day, and it's going to take them weeks to acclimate. That is a non-starter. It is never going to happen. But Thank you, biochemistry. We can turn on that third day of fasting freedom when you're in ketosis. We can do it in the morning and still get the benefits of fasting. So we can take someone who is obese, someone who has poor mitochondrial function, and we can make them fast the first morning without suffering. And over time, they get stronger and stronger and stronger. So let's skip the pain. This whole idea of self-flagellation for self-improvement, we've got to get over that. No one wants to suffer. And there is no merit in suffering, um, not when there isn't a need to do it. You only suffer—

I'm sorry, have you collectively met like road cyclists?

I used to be a road cyclist.

Road cyclists are the exception to this rule.

You know, that's a fair point. I mean, there's BDSM clubs too. There's a lot of commonality there, I think.

Fair enough. And it's, by the way, it's the same, right? They're both on the flow you get from endorphins rather than other sources, right?

I was just gonna say it's an endorphin thing that's going on there.

Exactly true.

There's also the hair shirt fasters or the hair shirt sect. You know about hair shirts? You probably would.

I do know what a hair shirt is.

You are the only person I have spoken to about this who knew offhand what that was, which makes me like you even more.

People don't know what a hair shirt is?

Dude, most people don't. It blew me away. I thought everyone knew.

What's a hair shirt?

Are you kidding? He's not kidding.

Most people don't know.

Stephen, tell them.

I'm not kidding.

It's a shirt that it's intentionally made super itchy with wool and other animal—

It's made from human hair.

Monks would wear them as punishment because you can't— there's so much contact with the skin that you can't forget that you're wearing it. It doesn't automatize. It's itchy all the time.

Yeah, suffering has merit and you're a bad person, therefore you should suffer, and suffering is the path of progress. And if you believe that, you can do a water-only fast when you're heavy and try to work and try to deal with your life, and you probably will quit fasting after about a week, and then you'll say that didn't work. But if instead you said, I know how to take the edge off, in fact, I know how to remove the edge entirely so I feel better than I did before the first time I tried this, suddenly, like, oh, I can do this. And if you use the tools to help you get acclimated, all of a sudden, like, I can have breakfast or not have breakfast and my life won't change. I won't think about food. People put a donut in front of me and I won't have to deny myself the donut using willpower. You just don't want it because you know that if I eat that, I'll have less energy. It's just not attractive anymore. That frees up 15% of the thoughts in your brain according to a study that's in Fast This Way. Because, you know, Stephen, you and I are both heavily into neuroscience and all, and I didn't actually read how they quantified it, but they found that 15% of the average person's thoughts— this is average, not metabolically unfit— person's thoughts are about what's for the next meal. If you get 15% of your thoughts back, that's kind of a big performance upgrade.

That's amazing. I can't actually believe people spend that much. I have never spent more than, you know.

Yeah, but you've never been hungry.

Yeah, I can empathize with that statistic, Dave, for sure.

What— so in terms of adjustment, I've never seen anybody actually eat like Rian, so it's true.

But I fast though, that's the, that's the key.

You do.

It's true, you eat 3 meals per meal, but you fast.

Exactly, exactly.

That's totally fine. If you fast, you're supposed to eat 3 meals for your one meal of the day, right? You got to get enough food in there. If you chronically are too low on calories— calories are how we measure energy. Like, everyone's like, I want to be on a low-calorie diet, but I want lots of energy. I'm like, guys, can you do math? Calories are where energy comes from. It's okay to eat, just don't eat all the time. You'll be fine.

Dave, you mentioned different tools that you can use to, you know, minimize suffering when fasting. I'd love you to break down some of those tools for folks who are interested in fasting. And then also, maybe you can speak to the role that just fasting frequency also plays in minimizing suffering with fasting. I know I've found personally that just the more you fast, the more energy you have while fasting and the more untethered energy becomes from food over time. So yeah, what are some of the tools and then how does frequency itself play into that?

The best tool that I learned from Steven's work is terror. 'Cause if you ski really, really fast, then you can't think about food and you're totally good to go. Okay, maybe not.

Just ski when you're fasting.

This is Stephen's theory of life, I think.

Exactly. Now, there's, I'm gonna say 4 things. In the book, there's 3 I identify, but having talked about this with, we have about 28,000 people doing a fasting training where I'm actually teaching the book to people. That's at fastestway.com. People can sign up, it's free. It's just a gift for readers. But what I found is that the easiest thing you can do is have dinner a little bit earlier, because if you had, say, finished dinner at 6 and then you don't eat dessert, it goes from 6 till 10. That's 4 hours. You sleep for 8 hours, maybe that's 12 hours, and you wake up at 6 a.m. If you have breakfast at 10, you just did a 16-hour fast. But to your mind, You really just kind of had breakfast a little bit late. It's pretty darn manageable. So that's one of the things where maybe it's not as bad as you thought, cause you were asleep most of the time. And that though may create low blood sugar or that feeling of being cold that a lot of people get when they start fasting. And for me at 300 pounds, I would have been unable to do that because I would wake up with this gnawing hunger. So then how do we turn on energy in the body? And there's 3 things that massively change your response to fasting that you're allowed to do during a fast based on science that are offensive to the hair shirt fasters. The water-only club gets very mad because mice only had water when they did a mouse study, therefore humans should only have water. I do not believe that. There is merit to water-only fasting. It's certainly not the only way to do it. So the first thing that massively improves a fast is black coffee. So here's why black coffee actually works. It's because the study that came out at UC San Diego a few years ago found out that the amount of caffeine in 2 small cups of coffee doubles ketone production. And that's really useful because when your ketones go up, this is when your body starts burning fat. When they go up just a little bit, far below the nutritional ketosis levels, it has an effect on a hunger hormone called ghrelin. And it drops that and it raises a satiety hormone called CCK, which was invented by Calvin Klein.

That dry delivery. Most people now don't know what satiety is. First of all, they don't realize you're saying satiated, not hungry. And so they really think that Calvin Klein invented this thing.

Because turning down hunger is different than feeling full, right? Like they're actually different feelings.

Dave, hold on. I need a clarifying question. Is this what you get when you buy the Klein underwear? Like the— you get the white tight briefs that they used to wear in the ads and you get this diet?

If they're tight enough, it works.

Okay. It's bundled. Okay.

Yeah. Thanks.

Now this is why they don't let David and Steven in the same room at the same time very often.

Yeah. They usually have to have guards posted when that happens. So this change that happens in hunger hormones just from black coffee, it's relatively mild, but there's lots of studies that show that coffee reduces hunger anyway, and this is the likely mechanism we just didn't understand before. So this is step 1. And for someone who's looking at Zoom right now with their kids around and they're saying, I'm gonna have only water, or I'm gonna have a cup of black coffee, they will be much more likely to complete their fast if they have black coffee. They will feel better, their brain will work better, they'll be happier, and they won't want to punch people. It's that straightforward. Now That isn't enough though. If for me, when I was heavy, I was hitting the coffee, don't worry about that, but it's going to take more as people get going. The second fasting hack, and there's new science to support this that I couldn't have written about because I hadn't funded any research on it way back in the day, and that is you can do Bulletproof Coffee. Bulletproof Coffee, yes, I am well known for this. No, it will not change my life if more people decide that they're going to try Bulletproof Coffee. It will change their lives, which is why I'm talking about this. Bulletproof is a very successful company because I like to think it works. So what this is, is the mold-free coffee beans, grass-fed butter, and Brain Octane, or Bulletproof MCT. It's a special form of MCT oil. Since I wrote the original book on this, two major studies have come out about this. One of them shows that the specific form of MCT oil I've been recommending for 10 years, it quadruples ketone formation. But the most common, cheapest, and abundant MCT oil that's out there— because there's different types of oils that can be called MCT— it doesn't raise ketones any more than any other fat. So you have to get the right thing. What's happening here is a mild bump in ketones from coffee and from this MCT really seriously turns on the same type of brain energy that monks are looking for on the third day of their fast, but you get it the first morning. And the other effect that's really, really necessary for fat burning that I could not explain, that drove me nuts, is Goes back to when I first had yak butter tea at 18,000 feet elevation in Mount Kailash. Okay, if you're a small Tibetan person, all of your possessions have to be pulled by a yak. Why would you every morning take a scoop of yak butter and a scoop of tea, put it in a butter churn that you carry around, and then churn it for 10 minutes before you drink it? Wouldn't you just eat the butter and drink the tea and save the dishes, given you don't have running water? Well, they don't. And for thousands of years, they churn their yak butter tea, and it doesn't make any sense as an engineer, and it makes me mad. So I gave $50,000 to the University of Washington, and I said, can you figure out some water-lipid interaction chemistry stuff? I don't know what you're going to do with this, but I know what you're studying, and I think there's merit here. So Dr. Gerald Pollack, who's written several books on phases of water, has identified a fourth phase of water where when you drink water today just normal tap water or whatever you like to drink. Your body puts the water near your cell membranes, which are made of tiny droplets of fat, and then it heats the water at 1,200 nanometers. It's called body heat. It's not that magic. So after a little while, the water changes its viscosity, its thickness, and that water is the water that your body uses to fold proteins, to make ATP, and to do all biological activities in the body. And Dr. Pollack is at the University of Washington, and he's, I think, about 80 now and has spent decades looking at water-lipid interactions in biological systems. So here's why the Tibetans blend their yak butter tea. Dr. Pollack's research— and by the way, this isn't like magic fairy water. This is— you can see it on a microscope, like it looks different, so it's very noticeable. And he says that what is definitely known is that butter oil, grass-fed butter oil, that was the fat found in butter, when it is exposed to water, especially hot water, or I don't know, maybe say, dare I say coffee or tea, it could be either one, and you blend it, it changes the structure of the water so that the body doesn't have to heat the water in order to start using it to burn glucose or ketones to make energy. This is why the Tibetans do it. It's cold and there's no air, so they're, they're taking that function out of their body and They're putting it in their tea, they drink the tea, and they can very quickly use that water in order to start making ATP. So when you're feeling groggy in the morning, you blend— and I'm talking, you can do a half a teaspoon of butter, it doesn't have to be a lot. You might want more, especially if you're using the butter as a building block for new cell membranes, if you've been a vegan or something and you're working to, to fix your cells. But what's going on there is the water in the coffee can more easily be used to make energy, and that energy can be pulled from your fat cells, and it can be pulled from any other source of food that you eat. But you feel different when you do that. So now you've raised your ketones and you can more quickly use the ketones to make energy. So you drink it and 15 minutes later you go, oh, I've got it this morning. And then someone puts a muffin in front of you and your cells have more energy than they're used to because they already got water, they got ketones, which have more energy in them than glucose anyway. And you actually don't really want the muffin. You have like a, a vestigial response, oh, food, should eat. But then you go, but I'm not Actually hungry. Hmm.

I think there was a fourth one there, Dave, as well.

There was another one, the fourth one, and this one has never been written about in any book on fasting because it would have been really easy to write a book on fasting. Step 1: don't eat for a while. Step 2: it's good for you, here's some studies. And like, there you go. And there's good books out there that make the case, and I do make the case scientifically, but you don't have to repeat that over and over. Logically, we all probably can be convinced that it works, but we won't do it. This is the book about how to actually do it based on a lot of experience, not just personal, but with with hundreds of thousands of people using intermittent fasting for a decade. What you end up with in this fourth one is prebiotic fiber. And this is neat. It's a kind of fiber, soluble fiber, not Metamucil sawdust kind of stuff. And what it does is it goes into the body and the body cannot digest it. So it goes into the gut and then the gut bacteria are like, oh, I can eat this. And when they eat it, they turn it into short-chain fatty acids called butyric acid that's anti-inflammatory and pro-ketogenic. So I will just put it to you that there is no one on earth where if you give them a coffee with a little bit of butter, it can have more if they need it, MCT oil and prebiotic fiber, if they drink that, there's no one on earth who's going to look at a muffin an hour or two later and go, I really want to eat that. You're actually sated. You don't want food. The voice in your head about food goes away entirely. But then people go, but Dave, there was calories in there. There might've been up to like 75 calories or 100 calories. That's not a fast. And we go back to the hair shirt, water-only thing, and then we look at the experts I've interviewed about this, and we look at the mechanisms that are happening during fasting. There's 3 big things that are going on during a fast. One of them is your insulin doesn't go up. None of these things raise insulin at all. Some guys a while back did a study of 300 different breakfast opportunities or different breakfast types to see which one raised insulin the most and the least. Bulletproof Coffee didn't change insulin at all. It was the number 1 choice for I don't want my insulin to go up. Having consistently high levels of insulin is bad for you. So there's insulin and there's eating protein. If you eat protein, it raises something called mTOR in the body, and mTOR is a signaling molecule that says grow. And what you want to do when you're fasting is you keep this mTOR low, and mTOR is like a spring in the body. So what you do is you push the spring down and down and down, and then when you do things that allow it to raise, it spikes very high. And people who live a long time have mostly low, but they have high spikes because when you spike mTOR, you put on muscle and you get bone density and your brain can grow. But if it's chronically elevated, you get cancer and you get inflammation. And this is why a lot of people who are bodybuilders don't make it far past 60 because they have chronically elevated levels of mTOR. So the idea is, how do I get the spike but not deal with it the rest of the time? Intermittent fasting works well for this. And what's cool is there's 3 things that push mTOR down. One of them is intermittent fasting. Another one is coffee, and another one is exercise. So there's a chapter in Fast This Way about how to stack all those things together. And what you do then is you have an early dinner, go to sleep, wake up, don't eat breakfast, have coffee, and then later, before you decide to have lunch, workout. And the workout can be amazing. It can be, you know, 30 or 40 air squats and some push-ups. It doesn't have to be crazy, anything like that. And then when you eat, you can have protein, which is gonna raise mTOR. You can have something that raises your insulin, but not sugar and crazy stuff. You can have some carbs if you want to. This doesn't have to be ketogenic. And suddenly what happens is your mTOR goes through the roof, and then that exercise causes change in your mitochondria and in your muscle density. But then it goes back down again because you give your body these rest periods where it's not putting energy into digestion, so it can put the energy into cleaning the cells. So it's really elegant how all this works together. But if you do without suffering, it's easier than what you do today.

Hey, it's Joshua with the production team. Thanks for listening to Flow Research Collective Radio. Before we dive back into our conversation, there's something to consider. It may be that today we are under-challenged. We're drowning in comfort. Now, in his book Antifragile, statistician Nassim Taleb pointed out something that's of key importance. Quote, undercompensation from the absence of challenge degrades the best of the best. The best horses lose when they compete with slower ones and win against better rivals. Now, put another way, who we could be, or our highest potential, is squandered by safety, coddled by comfort. If you want to train with us at the Flow Research Collective, it will require boldness. But what's life without a little adventure, right? To learn more about how you can get more flow in your life and achieve your professional and personal goals in less time and with more ease, Go to getmoreflow.com. If you're a good fit, we'd love to train with you. All the best.

What if it's not 6:00? What if it's 7, 8? Meaning, do you lose all the benefit if you shrink the intermittent window? Is this to maximize benefit? Is there something that turns it on, turns it off?

There's two answers to that. One of them is about the timing of the window and the other is about the length of the window. The minimum effective window that's shown in studies is a 12-hour fast. Just about anyone can do that. It is not nearly as effective as a 14 or 16 or an 18-hour fast, but it's totally okay to start there if that's where you are, especially if you're in perimenopause or if you've got some extra weight. You know, you can do that and slowly over time it becomes easier. It's sort of like if you haven't exercised in a while, you go for a walk around the block and you're winded, so you just do that. And you wait 6 months and you're walking 3 or 4 miles until you're winded. So exercise and fasting are similar in that you can absolutely improve over time. It's a practice thing. It builds strength in the body and in the cells and in the willpower. All right. So that was one of your questions was around the length of time that you need to go without food. The second one though is about when should you eat? I interviewed Sachin Panda. From the Salk Institute about, geez, 5 or 6 years ago and went to his lab there and looked at, you know, rat mitochondrial cells in the retina. And that knowledge and a bunch of other research, including my company called TrueDark that makes glasses to modify circadian biology that are not just blue-blocking glasses, what you end up with is you realize there's a signaling thing happening in the body for timing of sleep. And light is the most powerful signal. And with light, there's 3 variables. It's angle, color, and radiance, how bright it is. So you can modify those 3 things. But the second signal that is almost as strong but not as strong is food timing. Think of it like this. There was a time 2 billion years ago when we were ancient bacteria floating in an ocean. And what we would do is We'd get cold and dark. By the way, temperature is the third signal in terms of strength. We get cold and dark and kind of settle down in the ocean, and then the sun would come up and we'd see sunrise colors. And as that happened, photosynthesis would start in our food supply, these little algae. And then as the sun was coming up and it's right overhead, we get heat, we get light, and the food starts to be most abundant between noon and 2:00 PM. And if you, you would have maximized your calories then, and then the sun starts to set, and then the colors change, and then the temperature drops, and then you, you start resting. And that's when you would basically process the food and do your self-repair. And we would do this over and over. Same thing is going on with the idea of making sure that your fasting window is when the sun is down. When the sun is up is when you should eat. So don't eat after the sun goes down is a massive rule. And maybe you don't even intermittent fast. Even on days when I'm not going to intermittent fast, I still don't eat after the sun goes down because it makes such a difference in your energy levels. It, it's one of the cheapest things you could ever do. Move dinner earlier.

That makes sense, Dave. Uh, you cover this really well in the book, so folks should definitely check the book out for this. But could you give us a breakdown, Dave, of different types of fasts? You already mentioned a water-only fast versus coffee and, or Bulletproof Coffee, but different types of fasts and then different lengths of fasts and what you recommend. People do in terms of, you know, stacking or setting up their sort of fasting schedule?

Look at the meaning of the word fast. It means to go without, and there is no rule that says what you're going without. You can fast from carbs. It's called the keto diet, right? You can fast from healthy fats. It's called the vegan diet. Um, you know, there's all kinds of, of different things that are possible. You can fast from alcohol, you can fast from sex, you can fast from social media, you can fast from anything that raises dopamine. And I talk about those. So the strongest and most difficult fast is actually fasting from hate. I try to go 4 hours without thinking one bad thought about yourself, other people, or other things. That is exceptionally difficult, but it is a fast. It's just teaching your body to be safe going without something that it thinks you need. You can also fast from air for brief periods. That's called breathwork. And when you breathe out and hold your breath empty, the body is like, I'm going to die. And you're like, shut up, body. You're not going to die. You could probably go 2 minutes this way. So I'm just going to teach you to be calm in a state where you thought you needed. And a lot of fasting is really the body sends a signal that if you don't eat that taco right now, it's the end of the world. And you're like, but I know I could go 60 or 90 days without food. Why do I feel like I'm going to die if I don't get something that I know I don't need for 2 months? And it's sorting that out that is the trick of fasting. So those are different types of fasts, and then there's different lengths of fasts. One other type of fast I'm gonna call out is called the Bulletproof Protein Fast because I introduced it in 2012 and people are still doing it, and I mentioned it in the book. There's a body of research that shows if you eat less than 15 grams of protein from all sources— and keep in mind, vegetables have protein too, you have to look it up online— You can eat and it will mimic the effects of a fast. There's also things like probably the godfather of fasting, Valter Longo, talks about the fasting mimicking diet. What, you mean you can eat something and still be fasted? Well, you're certainly getting the benefits of fasting. So is that a fast? I would argue yes, it is. So there's a protein fast that's involved. Just don't eat the protein. 12-hour fasts are the minimum, and if you're only going to do those and that's your, your upside goal, that's probably not going to work. But it might be great, especially for women. And there's study of women particularly found that they were doing better on 3 days a week of 12 to 18-hour fast depending on their preference. That study's out of Australia. So the idea here is you can go 12, 14, 16, 18 hours without food. There's also something called OMAD, which sounds very manly. I'm doing OMAD today. But it just means that you have one meal a day. In other words, it's a 23 or 24-hour fast. And from there we go into multi-day fasts, which you can do as well. And the benefits of intermittent fasting are so strong that I think it's great to once a quarter go for maybe 2 days, 2.5 days without food. It sounds incredibly painful and annoying. Once you've learned how to intermittent fast, it's not a big jump. You can use the fasting hacks from the book during that time, and at the end of it, like, I was mildly hungry and a little bit low energy on the second or third day, but it was It was completely manageable. There's also a spiritual fast that I write about in the book because what I did— I'm like, wait, I'm afraid of being hungry because if I'm hungry, I turn into a jerk. And I'm afraid of being hungry because if I don't eat 6 times a day, I'll go into starvation mode. I know, I read it in Reader's Digest in 1980 and I believed it. So from all of that perspective, like, there's a background anxiety that's in there. And I also— I was afraid of being alone. I knew that I'd eat if I was lonely, so I hired a shaman to drop me in a cave on a vision quest and I spent 4 days with no food and no people anywhere for 10 miles around.

Hey Dave, couple of quick questions for you. For almost probably 20 to 25 years, I've done exactly right. I eat before dinner, I don't tend to eat after dinner, I tend to get up and start working at 4 AM, I don't tend to eat till 9 or 10 o'clock, and I always hike my dogs up a mountain before I eat breakfast. And I've been doing this forever. Here's my question: And what I've noticed over time is that when that morning workout— because hiking my dogs up a mountain is not often my workout for the day, right? I'll go to the gym, I'll go skiing, I'll do something else later. But I find that if I go really hard in the morning after fasting, that's my primary workout, right? Kind of thing. It is hard, no matter what I eat, to get energetically back to where— like, I can't get my brain clear. After eating to— like, if it's a big workout, I can put my big workout later in the day. But if I use that— if my morning workout is heavy, I don't seem to be able to get my brain back to where it can be. Whereas if the— and I can't tell if that's me, just my biology, my personality kind of thing, or if that's a thing.

But you're eating after your workout, right?

Totally.

So here's what's going on. It's possibly a cortisol thing. 'Cause you're a bit of an adrenaline junkie and adrenaline and cortisol kind of go hand in hand. So that's possible. But when people overfast, they tend to get this problem. And this is a big thing. Oh, if fasting a little bit is good for me, I will just eat one meal a day for the rest of my life. In fact, I'll eat one meal every other day. And eventually there's a word for that. It's called starvation and it raises chronic stress. And then you start getting more and more cortisol. But what I think is happening with you is that let's think about what happens when you eat. So you put food in the stomach. Now, your body has a set amount of enzyme potential and ATP— this is electrons, basically. And when there's nothing in your stomach, all of the electrons that are available in the body are going towards thinking and repairing and doing stuff. And as soon as you put food in your stomach, it now says, oh wait, I've got to go digest that. And digestion actually takes energy that could be going for thoughts. And this is a real thing, like there's a net energy equation in the body.

Oh, for sure.

And then you see swings in your blood sugar, right? So what I'd want to do is I'd want to put a continuous glucose monitor on your arm and see what's going on. Are you getting a blood sugar spike and then a blood sugar decline afterwards, which happens for some people? And it may be happening with you I'm assuming you track your heart rate variability. How are you doing there?

Pretty good, though it's been a while since I've tracked my heart rate variability. You like to track things a lot more than I— I don't like to track things. I like to— it's too much. I'm just too busy.

You know what, I hate tracking things. One of the rules in my Game Changers book is track what you hack. I like to control things, so I will track things that require zero work to track. Otherwise, I only track them when I'm working on it. Right, exactly. So I do know my heart rate variability because I sleep with a ring, and my Oura ring tells me every morning without me having to do anything. And I consider that to be one of the most important health things, where knowing your sleep quality and your heart rate variability. So if you're chronically stressed, I would say it's one thing, but for you, I think it might be worth knowing your blood sugar levels after a meal. But most likely what's going on there is you're just used to having a brain that's fully powered, and then you eat and you get this kind of a food coma. I also suspect, having hung out with you a few that your nutritional choices may not be the most optimal on the planet. Are you eating super healthy things or are we eating buckets of fries?

Oh, my super healthy. I've always eaten super healthy.

Really? I thought I remembered a lot of beer.

No, you know, not with me. You really didn't.

I really didn't. Okay, cool. I could be remembering it wrong. I remember this bar.

I remember this green bar. I remember that. And by the way, there was no beer. I drank bourbon. I don't know what you drank. Bourbon. Oh, sorry.

Yeah, it started with a B and it was alcohol.

No, no, no, no. By the way, David, I don't in general like people and like being in public. So when that does happen, sometimes there will be alcohol involved, especially if I don't know the people.

Okay. But it's not a regular practice then?

No, I very rarely drink.

Okay. I'm in the same, the same, but I like it to be older than I am, which means I have to regulate how much I would drink because I would go broke drinking that kind of stuff. So I'd rather have one drink of something really good. On a rare occasion than 3 drinks of something pretty good. So that's not the variable there then. So yeah, I think what's going on there is just you're used to having a brain that's on full power, and when you eat, after you eat for a couple hours, the power is going into digestion, and eventually it'll return to you. But something else happens when you eat. It's almost like you have an infection. Your body has this huge wave of white blood cells, these monocytes, that actually cause inflammation, and they go throughout the body, and you get a little bit of a spike in inflammation that happens when you eat. It's one of the reasons that eating fewer but bigger meals every day has less spikes of inflammatory molecules. And that's the most likely cause of it, is that your body is saying, I needed the most energy right now post-workout, and I'm putting the energy that I have into dealing with what you just did to my muscles and digesting. So you're gonna think a little bit less for a couple hours, and that's just how it's gonna be.

Dave, two more questions on types of fasts. One, you mentioned dopamine fasting, which I want to come back to in a second. But in terms of excessive fasting, how do you know it's excessive or what would you say is excessive? And I'll ask another, just a quick personal question as well. I've been doing a 48-hour fast from a Sunday night to a Tuesday dinner time every week for the past 7 or 8 months, which I'm now thinking may be excessive. But how do you know and what sort of frequency tends to be optimal for people?

Are you combining that with intermittent fasting on other days?

Yeah, yeah, I do kind of a 6-hour eating window every other day, the other 6 days.

Wow, you're probably on the edge, if not— you're kind of doing elite Olympic athlete training schedule of fasting. Not that elite athletes should train that way, but if fasting is exercise, you're pushing yourself pretty hard. It varies by age, it varies by gender, but here's what happens when a person starts fasting. Oh my God, it feels so good. If it feels good, more is better. And then when things start not working, well, clearly I'm not fasting enough. So then they fall into this trap of doing it more and more because it stopped working instead of doing it less and less until it works again. And this is just human nature. So for men, it usually takes about 2 months of overfasting for symptoms to kick in. And one of the first symptoms that you find is you wake up and you feel like you didn't sleep. So you're groggy in the morning, you don't feel well recovered. And if you were to measure your heart rate variability on a Ring, it's going to be lower. And the second thing that happens is you wake up without a kickstand. And so you're like, you know, things aren't kind of working the way they did before. And the third thing that happens is you start seeing hair thinning. And So that means that you need to back off a little bit. Maybe you need to add some carbs in your evening meal. And for women, it usually happens between 4 and 6 weeks. And then it is, um, poor sleep. Then it's a messed up monthly cycle. And then it's hair thinning. And you don't want to get even to the second stage of that. And here's a neat piece of advice for everyone listening. And this is why it was worth writing a book about this. This is like the practical stuff, not the, here's the study that says it's good for you. If you look at your sleep score or you just wake up, you're like, oh God, I feel like I didn't sleep at all. That might not be a day for a long fast and heavy workout. So I was up till 3:30 AM last night because I was on a UK morning show. It was the only way to do it. So this morning, guess what's in my Bulletproof Coffee? I put 40 grams of collagen protein in there. I'm not fasting this morning because when you eat protein, you break a fast. I intentionally decided not to intermittent fast, which is my normal morning practice, because I know that I basically literally punched myself in the face from a circadian biology perspective last night so I could talk with a bunch of people in England who are apparently offended at the idea of skipping breakfast. Go London! And that means, should you eat if you got bad quality sleep? Yes. And this means that fasting should not be the same every day. It should be based on how you did. Did you like hit it really hard at the gym yesterday? If so, you probably should have breakfast today. It shouldn't be Cocoa Puffs, but it should be high protein and high good fats. And that's going to allow your body to use the protein when it needs it most. So that's the other reason I'm having protein is yesterday I lifted. So geez, I didn't sleep well and I had extra biological stress yesterday. Today is not a fasting day. So fasting should not be the same every day. This is true for men and it's doubly true for women. And that's why I put a chapter for women in the book that's specific to female biology, because a lot of the fasting studies just say, oh, women are basically miniature men. But biologically, there's some differences there, and they really matter. And women are also more sensitive to nutrient and calorie availability, because let's face it, if you're a woman in an area without enough food historically, a woman of any species, and you get pregnant when there's enough nutrients around, the odds of having a successful pregnancy go down and the odds of dying go up. So this is why women's stress signals are more finely tuned to nutrient availability, which is why fasting is so powerful for women, but it's also why they need to not overdo it. And guys, let's face it, from an evolutionary perspective, if someone were to get pregnant in a time of famine, we're less likely to die from it. And no man thinks that way, at least no men that I know, but our cells, our ancient bacteria pulling the strings, they all know that. And that's why we're allowed to be less stressed if we're hungry. And frankly, it was our job to go out and, you know, find a mastodon and bring it home. So this is why listening to your body and just giving yourself permission— today is a 12-hour fast, tomorrow's a 16-hour fast.

I've been trying to find a mastodon for a while to bring home.

Just go up to anywhere with tundra. It's all melting right now. There's tons of them.

I've got chihuahuas. I don't seem to find the mastodon.

I kind of want to see a video of you unleashing all of your chihuahuas on an ancient mastodon. It'd be like watching piranhas.

The chihuahuas, they will try to take down a cow. They literally— like, it is the craziest thing you've ever seen. You're like, do you understand, like, strike-to-mass ratios? Do you understand, like, trampling?

Or—

it's astounding. Yeah, if the chihuahuas run into cows in the backcountry, there are always like 5 or 6 of them that will go from herding to assault vehicle. And, uh, yeah, cows are scary. A mastodon would be terrifying.

Speaking of chihuahuas, I had a miniature dachshund, which is a kissing cousin, uh, to chihuahuas. In fact, I had a couple of them. One of them had some chihuahua and some rat terrier bred into his genes in order to make—

yeah, we've had a bunch of mini dachshund-chihuahua blends.

Yeah. And, uh, so personality-wise, you know, there's some differences, but our dog Merlin, uh, made it until he was 15 years old. He's the 6th dachshund I've had in my and he had no lipomas, those little fat nodules they get, no cancer, no bad health problems whatsoever. And he has been intermittent fasted for 13 of his 15 years. We'd feed him once a day, he'd get MCT oil in his food and collagen and raw meat and all the, you know, proper nutrients and liver and whatever else, but the healthiest by orders of magnitude. And, you know, from dogs get very food obsessed just like people do. Well, when we were using the intermittent fasting schedule and we were putting MCT oil in, which suppresses hunger, he wasn't food obsessed, but he stayed younger longer. And so intermittent fasting can work for dogs, but then they can eat the house if they're not well trained or if you're feeding them the wrong stuff. And this leads to the other part of Fast This Way. If you have a very hard time fasting, it might just be that what you ate before the fast was the wrong food. For instance, have you ever been just so full and satisfied after eating a big kale salad? Like, wow, I feel nourished. I don't want any more food.

With oil and avocado, you know, with oil and avocado on the salad, yes.

But if you load it up with fat, even, you know, crazy amounts of fat, you might do it. But if you ate the fat without the kale, you'd have been more satisfied, to be perfectly honest, right? So Kale is one of my favorite things to talk about there because we have problems with toxins in kale called oxalic acid. And there's 5 classes of plant toxins, and actually some animal toxins, but mostly plant-based, that drive cravings and hunger in people. So if you eat food that is incompatible with your ability to absorb it, it's no wonder that you'd be hungry an hour after you eat the food. So fasting will teach you— if I wake up and I feel like I'm gonna die if I don't eat It's what you ate that caused that. It wasn't random. So you start learning how to tune your food to work best for your own biology. And the rules are not the same for everyone. There's broad categories. These are probably going to be a problem for you, but eat a bunch of that and then see if a fast is easy, or eat none of that and see if the fast is way easier. And pretty soon you're like, wow, I never knew this, but this particular food makes me way more hungry than when I don't eat it. And pretty soon you start dialing your food in to work better for you. So then fasts become even easier.

Yeah, I found if I eat high carb before a 48-hour fast, it's crippling in comparison to high-fat, low-carb. And then, Dave, I know we got to wrap in a second. I just want to close the loop on dopamine fasting. Can you break that down for folks and some of the benefits associated with it?

I can. Dopamine fasting is the idea that I'm going to not do anything that's stimulating— spicy foods, sugar, social contact with people, social media, loud music, bright lights, anything that raises that pleasure chemical. So basically you're bored. In fact, gee, I wonder if fasting in a cave might be a little bit like that. But what ends up happening is that your body has dopamine receptors, and when they don't get any dopamine, they open up and they're more easily able to attach to dopamine later. So by periodically limiting your exposure to highly stimulating things, it makes everything else more pleasurable. It's pretty much the same idea that says, you know what, if you fast for 24 hours, when you decide to eat, it's going to taste really good, right? That's always your best meal is the one after a fast. Well, if you just take a weekend or a day, and sometimes people go longer and say, I'm not going to talk to people on the phone, I'm really just going to sort of just rest and reflect. That can have profound effects on how much pleasure and happiness you get from everything else you do in your life later. And the same effect is true of food.

Makes total sense. Thanks, Dave. We didn't get into fasting and flow. We'll have to save that for another one. Final question, Dave, which we, we like to ask folks on Flow Research Collective Radio, is our research genie question. So if you could click your fingers and instantly have the research get done, around any big question that you've been pondering, what would that question be?

Um, what is the fastest path to enlightenment for lazy people? If we could just solve that, it would be great. I see Stephen, he's solving it right now. I know.

Oh no, I was thinking that for a while it was like Highway 61, you know what I mean? Like, we had it solved for a while. We had that sort of laid Right.

In more seriousness, I would say we are missing some core science about how food affects our biology, and it is that food has 3 things in it. It contains energy, it contains nutrients, and it contains anti-nutrients. And this is because plants don't want us to eat them. And to date, most nutritional research has said if it doesn't kill you, don't worry about anti-nutrients. Only worry about calories, and for some reason we're supposed to eat food with less energy in it, and then worry about nutrients. And this line of thinking says, well, if you had a bowl of cyanide and you sprinkle a vitamin on top, well, it's high in vitamins, you should eat it. So I would love to see a lot more research over how these, these categories of food toxins are actually affecting us. For instance, mycotoxins— we know these are mold toxins that are formed as plants grow or while the grain and other things are in storage. We know that they massively reduce fertility and reduce cattle's ability to put on muscle, but we don't really track what these do to us even though we eat them. And there are many other things where they're, they're kind of small areas of research, and I put the 5 big buckets in fastest way, but I would like to see a lot more research around, okay, what do these do for the average person with average genetics, and what are the specific genes that make it worse for you? We are going to arrive at a world about 10 years from now where you actually have tools to help you know what food is compatible with you, because it is very clear that all food is not compatible with everyone. But we have evolved to eat a lot of crap to keep from starving. But since we're not worried about not starving right now, we're worried about actually living a long time and feeling really good. How do I know what's the right stuff for me? I think there's some core research to be done there.

It's a cool answer.

Nice. That makes total sense to It was super good seeing you, Mr.

Asprey, and hopefully soon in person.

Well, I'm looking forward to that as well, Stephen. And I also, I've got to thank you. Your book is awesome, and I believe we will be sharing the New York Times list together because your book is worthy of that.

It'll be very exciting. Thank you very much. And by the way, there is that ski resort on Vancouver Island. I know it's there. I'm coming for it.

My kids were there 2 days ago. So yeah, Mount Washington. Come on, come on up. The skiing's great.

I'll see you soon.

Where can people grab Fast This Way, Dave?

Yeah, Fast This Way is the new book. Go to fastthisway.com and I will teach you the book for 2 weeks at no cost as a gift. And just pick it up wherever you like to buy books. Amazon has it, Barnes Noble has a special edition with an extra chapter in it. And if you can support an indie bookstore during the pandemic, that is the best thing you can do as a human being because we need to support every small business we can. So thank you for reading the book. I promise you it's more than worth your time or I wouldn't have written it.

Yeah, guys, it's good. It's worth reading. Everybody should check it out. It's really fun.

Thanks, Dave.

Thank you so much.

Bye, guys.

Hey, it's Joshua with the production team. Summer's here, things are heating up, and ice cream is calling. But imagine that instead of just getting to enjoy ice cream, you had to run an ice cream business. Meet Nikki Schroeder, a recent graduate of Zero to Dangerous and Chief Revenue Officer of High Roadcraft Ice Cream. Nikki runs the fastest growing ice cream manufacturer in the country. Before training with us at the Flow Research Collective, her life was understandably hectic. Running the company, taking care of her family required Nikki to be on her feet nonstop. As she put it after finishing training with us, quote, Zero to Dangerous has given me powerful peak performance tools for me to take back control of my life and find balance in my hectic lifestyle. Now we're delighted that you got so much out of Zero to Dangerous, Nikki, and we wish you nothing but success with your business. If you're listening in, you want more control, balance, and flow in your life, come train with us. Just go to getmoreflow.com. That's getmoreflow.com. All the best.

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