by Dave Asprey
BREAK THE RULES AND BREAK THE FAST
Don’t be afraid to break the fast. The nature of life is cycles—think of the ouroboros—and if you teach your body to exist in one constant state, whether it’s a constant state of hunger or a constant state of carbohydrate access, you are training for weakness. You have to be able to eat flexibly, and you have to be able to handle your carbs.
People on long-term ketogenic diets and low-carb diets such as Atkins become insulin resistant over time, until they can’t handle carbohydrates at all. That’s not healthy or strong—in fact, it’s as damaging to your body as eating sugar and carbs all the time! Generally, I don’t eat breakfast—it’s a pattern that works well for me. But I will tell you, after more than ten years of doing this, that sometimes on Saturdays I have a nice breakfast with my family, even one containing carbs, because it tastes good. My body can handle it, because it’s become metabolically flexible.
I urge you not to become one of those inflexible people who thinks that you can turn away from carbs and never have to deal with them again. Don’t be a fasting puritan or a fascist or whatever word you want to use for it. This is real life. It is full of curveballs and unexpected pleasures. You have to be ready for anything. And I’m here to make sure you are. Imagine if I were a purist and said, “I’m just going to have my Bulletproof Coffee for breakfast, and maybe if I’m really hungry, I’ll put some collagen protein in there—but I’m never going to have waffles.” You know what? That behavior would actually make me weaker. If you find yourself going down the path of perfection, it’s time to spend a week on a “perfection fast” in which you deliberately eat imperfectly and go without fasting.
It’s a discipline to have some kindness for yourself and to also allow yourself some rule bending. Strange as it seems, a lot of people don’t believe in allowing simple pleasures into their lives. They equate rigor with achievement, and they never really live life as a result. The trap is that they get to the point where suffering feels good, so they keep doing it despite the costs. People who fast all the time will have exactly the same experience as people who are in keto all the time: a reduction in sex hormones, a reduction in thyroid hormone, an increase in cortisol and adrenaline, and a reduction in muscle mass.
Part of what makes the fasting trap so sinister is that nothing happens right away when you first fall in. Then, over time, the body pushes back. This is why it’s vital that you find balance in your fasting lifestyle.
THE IMMUNITY FAST
Given the wave of concern over the past few years about new and resurgent infectious diseases, people often raise concerns about whether fasting is a good or a bad thing when you are sick. The COVID-19 pandemic really brought those questions to the surface. Here’s the short answer: if you are metabolically flexible because you do regular fasting, your odds of getting extremely sick from any virus or bacterium decrease dramatically, because you are more resilient and have a healthier immune system. This is a powerful real-world example of what happens if you fast based on a balanced plan, strengthening your body and your mind without falling into the fasting trap.
Even if you have an active bacterial infection, studies show that avoiding carbohydrates and fasting enough to generate ketones is a good idea. You can recover more quickly if you don’t eat carbohydrates, especially sugar—with one really important caveat. If you fast for a long period of time, your immune system may not have enough energy to mount the ideal response. (This is yet another example of why obsessive fasting is not a good idea.) In this case, moderate protein and energy from fats are going to be a good idea. On the other hand, if you have a viral infection, studies show that glucose in your bloodstream helps you recover faster. But to be clear: you don’t have permission to pound a doughnut because you have the sniffles!
If you have a viral infection, eating moderate or even slightly higher amounts of protein, some slower-metabolizing starches, and maybe a few grams of glucose or sucrose could be good for you. Don’t overdo it with the sugars, though. It is well established that drinking a lot of fruit juice or soda or eating high-sugar foods can dramatically lower your immune function. In any case, having ketones present in the body is anti-inflammatory and always a good idea. During a bacterial infection, you can achieve this state through diet alone. During a viral infection, a moderate carbohydrate intake is beneficial, so the only way to have ketones present when you eat carbs is to use MCT oil or have a Bulletproof Coffee in the morning.
Flexibility and adaptability are essential parts of being strong. That’s true all the time, especially if you are already battling an infection. That’s why you want to practice moderate amounts of fasting, so you will remain resilient.
To summarize: If you have a bacterial infection, avoid carbs and continue moderate fasting. If you have a viral infection, eat protein, eat a moderate amount of carbs but not sugar, and use MCT oil. And especially during high-stress times, don’t give in to fear and despair. You have control over these things. You will be stronger and more resistant if you are in a good place psychologically as well as physically. Fasting can help with all of that.
Embrace life’s variety. Don’t fight the cycles of the world. And then you will sidestep the fasting trap and keep walking happily along your chosen path.
Conclusion: Fast in Peace
When I took my final hike around First Woman cave, my brain was on fire. Despite the desert heat and the rough terrain, I felt supercharged, as though I had a source of energy inside my body that hardly seemed possible. In hindsight, going off on my own along difficult, unfamiliar trails was a really bad idea. Terrible things could have happened if I’d gotten lost without enough water. But I was so charged that I had to move. Having that much energy violated my scientific understanding of the relationship between calories and metabolism. How could I be so powered up if I hadn’t eaten anything? Clearly there was lot more going on in my body—emotionally, psychologically, and biologically—than I had been taught.
In my elevated state, I felt so good that I decided I didn’t need my shaman to come get me. I texted Delilah, “Don’t worry, I’ll just walk back to the other cave. You can pick me up there. I have way too much energy.” Then I went back into my cave for the last time, packed up my meager possessions, put on my backpack, and said good-bye to my bees and the little brown bird. I was on a high, and I was unconcerned about the several-mile walk back to the other cave. It was a hot desert day, but I was carrying a little water with me. What could go wrong?
Well, when you get too cocky, life has a way of express mailing you a lesson in humility. I found my way out of the canyon to a dirt road, and then I made a wrong turn. I didn’t know the territory, and I headed for a nearby small mountain where I thought the shaman would be. As I searched for the trail I knew led to the cave, I found no trail at all. Just cactus and rough terrain. I climbed rock ledges, watching out for rattlesnakes. The sun beat down on my neck, and I was grateful for my hat. I drank half my water. When I got to the top of the mountain, there was no cave: I had climbed the wrong mountain.
There was almost no phone signal out there, and my battery was nearly dead. Fortunately, I’d had enough experience as a hiker that I didn’t panic. I called the shaman, tried to explain where I was, but “on a mountain in the desert, and I can see cactus” isn’t very descriptive. Still, I marveled at the strange energy coursing through my body, shattering my limited view of what my body could handle. I knew I could walk all day if I needed to. I climbed back down the mountain, enjoying the red cliffs, looking for a trail. There was no shade to give me a break from the intense desert sun, but I felt so good. I didn’t even think about food once.
I was still Dave Asprey, standing alone on top of a craggy hilltop in Arizona, but I was not the same Dave Asprey who had arrived at Delilah’s ranch four days earlier, dubious and full of anxieties. The old me had believed, at an instinctual level, that four days without food would create weakness and unbearable hunger. That four days without human c
ontact would stir up crushing sadness and loneliness. I had gone through some rough periods, true, but I had more energy now than before I had started the vision quest. I felt almost giddy. In hindsight, I know exactly what was going on: I had gone into ketosis, so I was burning fat and delivering concentrated energy to my brain. My body was also in a superclean state by then. There were no toxins in my body left over from eating inflammatory fats or proteins or sugar, so there were no digestion by-products clogging my brain.
Those are now well-documented effects of fasting, and it’s obvious that they were connected to the things I was feeling. But without a doubt there was a third thing going on: I had just experienced my first true spiritual fast. I still carried the scars of the old me, including the dozens of stretch marks left from the years when I had been seriously overweight, but I didn’t care about them as much anymore, and I appreciated the muscle that was emerging beneath them. The past held less of a pull on me than the future. Everyone should have a chance to experience this state, in which you feel absolutely free to live life on your own terms.
There was no cell signal at the top of the next hill or the second. I ended up walking something like ten miles in desert heat with a backpack and a mostly empty bottle of water, by myself after four days of fasting, and I was completely fine. It was crazy, and it was the best hike of my life. I felt so damn good.
I kept going, letting the universe take me wherever it wanted me to go, knowing that I was more than strong enough to handle whatever the universe brought me. And the universe delivered. I found Delilah right as my phone ran out of charge.
BE THE BEST MIRROR TO THE WORLD
As a kid I was an avid reader, and one of my favorite books was Homer Price,1 a collection of stories by the brilliant writer Robert McCloskey. In one of the stories, a traveling salesman named Professor Atmos P. H. Ear comes to town hawking an astonishing product called “Ever-So-Much-More-So” powder. You can sprinkle it on anything, and it makes it more of what it is. So you spread it on a squeaky wheel, it gets more squeaky. If you spread it on a beautiful tree, it gets more beautiful. It’s an empty can, of course, but people want to believe. The joke of the story is that Professor Atmos P. H. Ear is both a con artist and a sage. The beauty of the story is that people love his idea so much that they actually begin to see the ever-so-much-more-so effect.
Intermittent fasting acts like the Ever-So-Much-More-So powder. It enables you to be more of who you are and who you want to be. Fasting doesn’t guarantee that you’ll make the right choices. If you’re already kind of a jerk, you’ll have more energy to be a jerk. You’ll probably end up yelling at people even more than you did before. But if you’re earnestly working on making something good happen in your life, your community, or anywhere else in the world, you will do more of that, too. Fasting removes a lot of the obstacles in your way. One of the things in your way is all the energy you use to think about food. That misplaced fixation removes your peak abilities. If you’re always eating and digesting, some portion of you is always doing that thinking—or digesting—instead of doing something else. The pauses when your metabolism gets a rest are the times when your peak experiences can happen.
Step one in a meaningful fast is getting started. You have to push past all the obstacles that block people from even experimenting with fasting: “I might starve, it sounds like torture, it’s inconvenient, it’s weird, I might fail.” You are deeply programmed to avoid death and starvation, and fasting (or even thinking about fasting) will set off those fears. You need to put your modern, rational brain in charge of your ancient, instinctual lizard brain. Step two is using the fast to help you push past all the other obstacles in your life—the ones that prevent you from daring to travel or create or start a family or just be a better version of yourself.
I want you to examine your preconceptions about food and fasting and investigate where they come from. Why do you think they are true? What if a lot of them aren’t? Which ones can you actually prove? Many people resist fasting for even one day because of all the emotions it stirs up. They’re terrified because they don’t know what will happen. Well, here’s what’s going to happen: You are going to face the hunger. You are also going to face the fact that you may even choose to sit in a room full of people having a social experience called dinner, and that your plate is going to be empty. What emotional strings will the voice in your head play then? Is it going to say that you’re lonely, you’re not part of the group? Yes, it’s very likely to say those things. It’s lying.
Years after my vision quest at First Woman cave, I was invited to dinner at Kensington Palace in London. I was part of a group of senior executives who were meeting with some European elites. All very proper. As the tuxedo-clad waiters began bringing around waves of fancy food—the kind you’d expect to see served at a palace—I looked around to see what other people were doing. I had politely declined most of the food offered. I like to intermittent fast during business trips and would regularly fast for twenty-four hours around long flights to help prevent jet lag. Still, it seemed socially unacceptable to refuse everything offered to me at Kensington Palace, so I chose a few dinner items to be polite.
Amid all of the clinking of forks on plates, I was intrigued to see that the person seated next to me—Phil Libin, the CEO of Evernote—had nothing on his plate. I asked him what was going on. “I’m fasting,” he answered. He told me he was on day three of a five-day fast. He had just lost 80 pounds using fasts of up to eight days and ketosis. Back then, I couldn’t comprehend the idea of fasting at a lavish event like this, and I told him so. His response was that he traveled so much that the only way he could build fasting into his life was to decide that he simply was not going to eat, no matter where he was in the world. That totally resonated with me.
So we sat there with his empty plate and my half-empty plate, and we made conversation. You should have seen the reactions of the other people at the table. They were looking at him as though he was going to die. There was definitely judgment coming from people who had absolutely no reason to judge him. I overheard some people speculating that he had an eating disorder, even though he went through the meal perfectly happy and social.
I had a totally different take on what I was witnessing: “Good for you, man. You’re doing what you want to do.” He had the courage to fuel his own body in a way that works for him, and there are few things as precious as losing 80 or 100 pounds. You may have seen a similar reaction to Jack Dorsey, the CEO of Twitter and Square. We first communicated years ago about his intermittent fasting and coffee habits. Clearly, fasting has worked very well for him. Few humans can be CEO of two public companies at the same time. He says his diet is crucial for being able to pull that off. When he spoke openly about his use of one meal a day (OMAD) fasting, some media outlets tried to frame it as an eating disorder, just as people did with Phil Libin at the dinner party in Kensington Palace. When your diet owns you, it’s an eating disorder. When you own your diet, it’s part of how you manage your life. There is no way I could run a large podcast, write a book like this every year or two, and also be CEO of two companies if I did not practice fasting. It simply isn’t optional if I’m going to have the energy left at the end of the day to also be a good husband, father, and friend.
It’s almost as if the hungry voice in other people’s heads gets triggered when you decide not to eat. That may, in fact, be exactly what’s happening. Mirror neurons may make other people feel hunger when they see that you aren’t eating. That response once served an important adaptive function by making sure that hunters shared their kill with the rest of the group and by encouraging the whole clan to eat together and maintain their social bond. Today, however, it’s a cruel fact of nature that when you choose not to eat for your health, others often interpret your abstaining as their pain.
You might also be activating a social type of mirroring: when you make the choice not to eat, it can trigger other people’s insecurities about their own eating habits
(especially since we live in a culture in which so much shame is attached to food and body weight). Insecure people tend to operate without a lot of generosity; they may subconsciously or even overtly attempt to sabotage your efforts. You can do better, however. Once you understand where these impulses come from, you can handle any detractors with less judgment and more empathy.
I experienced these mirroring effects firsthand on a recent flight from Seattle to Dubai as I was writing this book. It’s quite a long flight, about eighteen hours in the air, and I was looking forward to the uninterrupted writing time. Once again, I was fasting on the flight to help stave off jet lag. As I sat down in first class (it’s expensive, but it also helps with jet lag), a flight attendant came around to offer me a menu. I smiled and told her that I didn’t need a menu because I wasn’t going to eat on the flight but that I’d love lots of sparkling water. Her eyes got big, and she insisted on handing me the menu, telling me I would need it when I changed my mind later. I explained that I really didn’t want the menu. She looked at me skeptically, as if she thought I might die if I didn’t eat for eighteen hours.
Those mirror neurons had her so worried that she recruited another flight attendant to try to get me to take a menu. Fortunately, the new flight attendant, Jacquie, was practicing intermittent fasting and used the Bulletproof Diet to help her handle the grueling demands of her job. She got me. Jacquie was happy to keep the menu and even supported my fast by brewing some coffee (with Bulletproof beans!) for me with a little butter in it.
One lesson I take away from such experiences is that fasting is so scary to the deep parts of our brains that we feel other people’s hunger and act to prevent it, often by sabotaging our own fasts or others’. But I also believe that empathy must work both ways. By letting the fast make you a better person and by radiating empathy into the world, you can lift up the people around you.