by Dave Asprey
Dedication
To my lovely wife, Dr. Lana, who is most definitely not
spending her time cooking breakfast anymore
Contents
Cover
Title Page
Dedication
Prologue: Fasting to Find Your Best Self
1. Fasting is Only in Your Head
2. Enlisting Your Molecular Machines
3. Many Stages and Many Styles of Fasting
4. Fast for Long Life
5. Fast for Better Sleep; Sleep for a Better Fast
6. Fast for Fitness and Strength
7. Fast for Mental and Spiritual Health
8. Supplements to Fine-Tune Your Body
9. It’s a Little Different for Women
10. Fast Every Way: A How-to Guide
Conclusion: Fast in Peace
Acknowledgments
Notes
Index
About the Author
Also by Dave Asprey
Copyright
About the Publisher
Prologue: Fasting to Find Your Best Self
The shaman’s instructions were quite specific: bring only a sleeping bag, a flashlight, water, and a knife for the vision quest. The first three items were critical for my survival. The last one was mostly for my peace of mind, apparently, because the biggest danger near my cave was coyotes, and coyotes don’t usually attack people. But on this kind of journey, there’s no simple boundary between physical and psychological well-being. Is there ever, really?
I had set off on my first vision quest in search of better health, greater self-awareness, and, above all, in the hope of achieving a deeper sense of peace. To an outside observer, I looked like a man who had found his success. It was in 2008, four years after my travels to Tibet and Mount Kailash, where I first learned about the mind-bending qualities of yak butter tea. There was a time when I wore size 46 pants and weighed more than 300 pounds, but that was behind me. After failing at every diet there was, I had invented a new one and had lost most of the weight I wanted to lose. I’d pushed myself into good physical condition. I was busily learning about ways to hack the body, seeking out new methods to radically enhance my energy, my abilities, and my longevity. I had already begun developing the concept for Bulletproof Coffee, the company I would start a couple years later.
Outside appearances are not what truly define us, however. On the inside, I was dealing with unsatisfied cravings in many different forms. I felt regular pangs of hunger, along with distracting yearnings for cookies, chips, and other low-quality foods. I would give in to those impulses at times and then quickly regret it. I was maintaining my weight, but I was not feeling in control of my body. I had worked hard on my personal development and extracted myself from a bad, self-destructive relationship. I now had a loving wife and a new baby. Here, too, though, my inner self told a starkly different story. I was not at peace. All my life I had wrestled with loneliness and had made some progress. Even in my seemingly idyllic circumstances, that sense of emptiness was always lurking.
At the time I was managing my life, but that was not enough. What I was searching for was a path to becoming bulletproof—to finding the unshakable inner strength that would let me become the master of all that I am, including the cravings for things that weren’t good for me. (The idea of becoming bulletproof later inspired my book and my company of the same name.) That search was what brought me to the shaman. I wanted to confront true hunger, to the point where I could free myself from food and all the ways it occupied my mind. There’s no way to fail at fasting if you’re alone in the desert! I also wanted to work through my loneliness by facing down the kind of isolation that comes only by completely removing yourself from human contact.
So I walked into a cave in the Arizona desert and away from the rest of the world. For four solitary days I consumed only water and maybe a little Sonoran dust. By the time I walked back out, I had experienced a fast that changed my life. By reading this book, you have just taken the first step toward changing yours, too.
The needs that drove me to my journey were unique to me, but they were also rooted in the kinds of universal human challenges that we all face. In my case, I grew up as a fat kid. I eventually learned that I had been exposed to toxic mold that triggered Hashimoto’s thyroiditis, a condition in which the body’s immune system attacks the thyroid, but I didn’t find that out until I was in my twenties. All I knew at the time was that I didn’t look like the kids I admired; with my teenage man boobs, I certainly didn’t look the way I wanted to.
If you struggle with your weight, and especially if you struggled with your weight when you were young, it’s hard not to feel judged by other people. Add to that some early childhood trauma or schoolyard bullying, and there may be a part of you that always feels alone. A common coping mechanism is to develop an emotional addiction to food, to rely on eating to soothe the hard feelings. I say all this without a trace of self-pity, because I know that everyone who reads this book has gone through his or her own versions of these struggles, even if he or she has never been overweight. Almost everyone has some form of physical or psychological addiction to food. Maybe yours is candy. Maybe it’s beer. Maybe it’s bread and cheese; gluten and milk protein are both highly addictive. Or perhaps you’re hooked on potatoes. Do you find it impossible to imagine life without French fries? I’ve been there.
The point is, addictions and cravings are built into us, even if you’ve never had a problem with your weight. They are easily activated, and there is a trillion-dollar food industry—what I call Big Food—that is specifically designed to do just that. When you’re bored, you eat. When you’re feeling stressed, you eat. Millions of years of evolutionary selection have hardwired us with these responses, as fundamental as our fear that things with sharp teeth might try to eat us. I sometimes refer to the four F’s of survival: fear, food, the F-word that involves reproduction, and friends. Without food, you would never get to enjoy those last two F’s, which is why the thought of going without food triggers such an intense, deeply irrational reaction before you even have time to think about it.
All of those thoughts were going through my head back in 2008 as I greeted the shaman and steeled myself for what lay ahead. Without being aware of it, I believed that even a single day without eating could leave me helplessly out of energy, which made me a prisoner to food. Going four days without food seemed a biological impossibility. This is how almost everyone in today’s society thinks. You can bet that if you ask ten people what would happen to them if they didn’t eat for a day or two, nine of them will say, “I’d starve.” They even believe those words.
By the time I emerged from the cave, I’d started to realize that none of this is true. I came to recognize that there’s a fundamental difference between hunger and craving. Hunger is a biological message, and it is something that you can control. Craving is a psychological need, and it is something that tries to control you. The truth is, you can go a long time without eating, and you won’t suffer for it. In fact, you will thrive.
The Big Food industry has worked hard to convince you that craving and hunger are one and the same. If every craving means that you’re about to starve, then you need to buy something to satisfy that craving immediately, right? And by a wonderful coincidence, Big Food is ready to take care of you with a candy bar that “really satisfies” and a thousand other processed drinks and snacks that shackle you to a relentless feeling of craving that subsides when you snack but never really leaves. The same dynamic plays out over and over every day, fooling us into thinking that we are prisoners to food. I wrote this book to help set you free and because no one wrote it for me when I was twenty-two and wearing size-46 pants.
GAIN WITHOUT PAIN
The key to that freedom is fasting—and learning how to do all styles of fasting without feeling pain, all the way from meal-skipping intermittent fasting to multiday fasts. What you’ll learn here contradicts almost everything people think about what fasting is and what it does. Intermittent fasting won’t make you weak, and it won’t cause you to starve. It also doesn’t require any one particular diet or one particular schedule of fasting, although you will experience a lot fewer cravings with some diets. Fasting is a tool kit that helps you unlock biological resources hidden in your body, resources you probably never knew you had.
Fasting can make you stronger and healthier, both physically and psychologically, by breaking you out of your food prison. It will free you from the burden of other people’s opinions about how you should feel and even of how your body is telling you to feel. Ultimately, it will help you live your best life—to be your best self, putting the most out into the world.
I know these are extravagant-sounding claims, but they are supported by an abundance of scientific research, ancient wisdom practiced for millennia on every continent, and by many years of my own experimentation. Our palette of fasting options has expanded greatly in that time. I’ve tried various kinds of fasts, and I will share my findings with you. But the most important message that you’re going to get from reading this book is just this: You can break away from the visceral feeling that if you skip a meal, or even several meals, you will be in danger—that you will be weak and miserable, unable to go on. You can overcome the feelings of fear, discomfort, starvation, terror, and loneliness, and replace them with liberation, power, and self-control. Work with me, and together we will make a better you. That matters more than whether you fast for a certain length of time or not.
Some of the things you want to change about yourself may be easy to spot. If you can’t see your feet when you look down or notice a muffin top when you look to the side, your metabolism is broken, and we can fix that. Other issues are subtler: maybe you don’t have the kind of energy and mental focus you wish you had. How many times a day do you catch yourself thinking about lunch instead of the meeting you’re in? Fasting can help you with that, too. Then there are the most insidious problems—the ones so ubiquitous that you hardly notice them at all. Even if you look and feel fit, you probably live with a background hum of fear. There is an ancient part of you that is always worried about what will happen if your food goes away, and, by extension, you fear all of the other things that might go missing. It is a subtle, pervasive, biological survival instinct, but you don’t have to let it control you.
All the way down at the cellular level, your body is programmed to think, “No matter how you’re eating—what kinds of foods, how often, how much—I can’t be sure what I’m getting will always be enough. Better store some extra.” That relentless message cultivates a broader mindset of anxiety toward all kinds of other needs in your life, emotional as well as physical. Training yourself to confront your anxieties (about food or other things) and master them may be the greatest fasting benefit of all.
In this book, you will learn the methods of intermittent fasting, but I will also help you understand the tremendous scope of what fasting can do to you and for you. You’re not ever going to choose to fast if you don’t know why it matters. And you’re definitely not going to choose to do it and stick with it if you associate fasting with suffering, misery, and deprivation.
When I came out of the shaman’s cave, I felt great. That was when I realized that fasting doesn’t need to be painful. It doesn’t need to be hard. It’s actually one of the most natural things you can do, because it is something that our species has naturally evolved to do. Fasting is a fundamental part of being human. After you finish this book and try some of these techniques until you find one that works for you, I am 100 percent convinced that you will like your life better than you did before—no matter what kind of diet you follow now, no matter what kinds of food you like to eat.
Remember what I said about intermittent fasting being a tool kit? I meant just that. It’s not a single set of rules but an entire program for hacking your biology to make it work better. You can still eat the standard garbage diet of fast foods every day, if that’s really what you want to do. You can be vegetarian, vegan, keto, Bulletproof, or anything else under the sun. Whatever type of diet you choose, if you eat your way in combination with the fasting techniques that I will describe here, you will be better off.
Here’s another big surprise: you won’t be hungry. Exactly the opposite. Intermittent fasting will set you free from hunger and all of the emotional baggage that comes with it.
Hunger heightens all your anxieties because it activates a powerful biochemical cascade in your brain. A lot of that action centers on a primitive brain structure known as the amygdala, which is about the size and shape of a small almond. That little structure is part of what Yale University neuroscientist Paul MacLean called the “reptilian brain”1 because of its primal nature. The amygdala handles rapid, automatic emotional decisions that help keep you alive when you’re not paying attention. It is the home of the “fight-or-flight” response that tells you to run away from a sudden lion attack or (more commonly these days) pull your hand away from a hot stove before you get burned. It can also trigger frightening spikes of hunger to make sure the body gets enough food—or more than enough, as the case was for me.
The actions of the amygdala were vital for our ancient ancestors, and they still serve a vital purpose in modern life. But as essential as the amygdala may be, it can also be a source of irrational, destructive fear. It’s a major contributor to that voice in your head that says you might just die if you do something you’re afraid of—such as going on a job interview, ending a bad relationship, speaking in public, or simply skipping a few meals.
Intermittent fasting enables you to put the amygdala and the whole reptilian part of your brain in its place, so that you can be more fully human, more fully yourself, less burned by your fears. When you start out, you might feel uncomfortable for a day or two. Then you will feel liberated. It’s not even hard. All you have to do is question a whole set of false assumptions about food and fasting:
What if it were easy to skip a meal—or two or three?
What if all fasts could be created equal?
What if you could eat and fast at the same time and have a better fast as a result?
What if you could use sleep and exercise to trick your body into thinking you’re fasting?
What if fasting could be personalized to your gender and your genes?
What if fasting could make you both physically and mentally stronger?
You can do all of these things. I’ll show you how. You can master your willpower and be in charge of yourself, more than you ever have before. Let’s go.
1
Fasting is Only in Your Head
To set off on a vision quest, tradition dictates that a shaman guide you. But how do you find a shaman? It would be great if I could tell you about a secret spiritual network, but the truth is, I tracked my shaman down by doing a Google search. In retrospect, it probably would have been smarter to seek out a personal referral or maybe do a background investigation before signing on for such a momentous rite of passage. What can I say? I was drawn to the experience, and I was feeling impulsive.
That’s not to say the shaman didn’t deliver, mind you. It’s just that some of her methods were . . . unique.
By tradition, shamans are rare, gifted humans who have attained a higher level of consciousness, enabling them to make a deep connection to the spiritual realm. The word itself gives you a sense of the tremendously rich history behind the practice. Shaman comes from the word sha’man,1 a spiritual figure among the Tungu people of Siberia. Keep pressing back in time, and you can trace the word all the way to sramana-s, a term for a Buddhist ascetic in ancient Sanskrit. Sanskrit! That goes back more than three thousand years, well before ancient Rome and Greece. Sanskrit was the language of many of the
primary texts of Buddhism and Hinduism. Nobody knows when shamanic practice first began, but there were probably shamans around—and fasting—when the pigments on the first cave painting were still wet.
Although I may not have known much about this particular shaman, I was well aware that I was tapping into a primal, powerful aspect of the human experience. I grew up in New Mexico, where I was as likely to see a cultural ceremony performed by an indigenous tribe as I was to experience Western religion. Later, I experimented with altered states and immersed myself in different types of meditation. When I walked into that cave, the most important thing I brought with me was a lack of preconceptions and a willingness to stay curious. If you truly want to experience the world, you need to keep yourself open to new experiences, including ones that come from beyond your own cultural background. Just be sure to approach other cultures with understanding and with respect and ask permission. Respectful inquiry has worked for me in the jungles of South America, in monasteries in Tibet, and even in the caves of Sedona. A good shaman will tell you to get lost if you’re not a good fit and won’t feel bad about it, either.
It takes an extraordinary mix of training, abilities, and background to become a shaman, but it’s easy for someone to claim he or she is one without doing the work. Ancient peoples chose their shamans by their ability to sense things that others couldn’t and put them through rigorous, often dangerous, training for years. Shamanic knowledge was passed down from generation to generation through that rigorous apprenticeship. Most shamans must experience extreme personal adversity and overcome it before they can earn the authority to help others. The help I was seeking was only half formed in my mind back then. I wanted someone who could lead a vision quest with fasting, to reset my relationship with food and loneliness, but I was aware of my spiritual and emotional hungers as well.
And then I met Delilah (not her real name; I’ve hidden her identity to protect her privacy). She owned a small ranch populated with llamas and alpacas. In her backyard, she had a sweat lodge equipped with LED lighting and subwoofers so she could play mind-altering sounds while sweating. Delilah was eccentric, for sure, but I was seeking out a guide who could take me on a vision quest, and I had a sense that this powerful, enigmatic, tattooed woman could get me where I needed to go.
