by Dave Asprey
STAGE FOUR OF FASTING MAY SOUND IMPROBABLE TO ANYONE WHO HAS NEVER DONE IT BEFORE.
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A fast that lasts more than 120 hours, or five days? Really? Yes, it is possible to live in ketosis for an extended period of time, if you are extremely attentive to your body’s needs.
At this point, you’ve entered the outer zone of fasting. Anytime you fast more than 120 hours, you are almost guaranteed to lose weight unless you have some really serious metabolic issues. There is a problem that comes with that weight loss: when you shed a lot of fat quickly, the toxins in your body—the ones from Big Food and Mother Nature, the heavy metals, the pesticides, the mold toxins that are stored in your fat—are all released at the same time. In response, you will get headaches, you will feel groggy, and you will yell at people. Be psychologically prepared for that.
During Stage Four fasting, you will enter a kind of altered state in which your body has switched over to burning only fat. People often describe a “fasting high” in response to this new metabolic reality of complete ketosis. You likely won’t need Bulletproof Coffee this far into a fast—your own inner furnace will be making ketones at full speed. It’s a good idea to have some quiet time. Most people can’t focus on really demanding tasks during a fast this long unless they’re quite well trained in fasting.
Your glucose, insulin, and IGF-1 levels have gone way down by this point. You have broken away from the cycle of insulin resistance, which could help fend off diabetes. Your appetite is suppressed to a low level, even as your body’s total energy expenditure remains steady. You don’t feel hungry, and you don’t feel weak, either. Autophagy is in full swing in your body, clearing out toxins and dead cell parts. Your mitochondria are working more efficiently, so they are releasing fewer of the reactive, destructive charged molecules known as free radicals. Elevated levels of NAD+ in your bloodstream help retard the continuous oxidizing of your cells. These mechanisms all have an antiaging effect.
Despite these benefits, you should be wary of trying a Stage Four fast. Some studies have shown that ultralong fasts can be beneficial for hypertension4 and may amplify the effectiveness of chemotherapy for cancer patients,5 but extreme fasting can be quite dangerous or even fatal. It can weaken the heart, suppress the immune system, and lower blood pressure.
Detoxing during long fasts is extremely important because of all those compounds set free during weight loss; I recommend taking activated charcoal to help with your detox. You also want to take supplements to maintain your electrolytes: calcium, magnesium, potassium, and sodium in particular. That’s especially important if you are doing a water fast or drinking just coffee and tea. You can get sick enough to require hospitalization if your electrolyte levels fall too low during a long fast. It’s a good idea to have a doctor supervise any fast that runs ten days or longer. I don’t recommend exercising during long fasts.
IN PRAISE OF INCONSISTENCY
You will notice that each stage of fasting affects the body in different ways and confers its own distinct benefits. That’s part of the reason why it is good to mix up your fasting styles. Some days, you just might realize that you don’t have the energy reserves to fast as long as you wanted. That’s okay, too.
Still, it’s human nature to think, hey, if something is good, surely more of it must be better! If you do an OMAD fast, you will feel great. You will feel strong. So why not do OMAD every day? Think about it this way: a piece of cheesecake is good, right? (If you’re not a fan of cheesecake, just substitute something else you love and roll with me here.) What about two pieces—even better? Uh . . . maybe. Now you are being served your third piece, and you might be starting to think, “Whoa, that’s a bit much, but I suppose I can try.” Four pieces, and you’re like, “Please stop.” But no, no, no! You said that more was good. You have to eat it.
You get the idea. People do this with vegan diets, they do it with keto, and they do it with fasting. It’s possible to get hooked on fasting, just as you can get hooked on any other style of dieting. I call it the “fasting trap” (see chapter 10 for more detail on this). Straight up, the vast majority of people will break themselves if they do OMAD all the time. You’ll feel great for a while, but then you’ll realize, “Something’s not right.” If you’re a woman, your cycle will feel off. If you’re a guy, you won’t feel your usual morning kickstand. These are signs that you overdid it. That’s why I recommend cycles of intermittent fasting: different cycles of fasting, along with breaks from fasting entirely.
Dieting books and fasting guides love to load you up with rules. Here’s what they almost never tell you: The body loves consistency because it needs to do less work to survive in a consistent world. The trouble is, when the body does less work, it gets lazy. If you send a signal to your body that the world is not consistent, it will rebuild itself to thrive in that world. That’s why your body will be much stronger if you deny it consistency: you will build yourself up by challenging yourself.
Natural selection exerts a tremendous evolutionary pressure on every creature to take in as much food as possible and expend as little energy as possible. Your brain, your body, the quadrillions of cells inside you, and even the ancient bacteria that merged with animal cells a couple billion years ago—they’re all telling you the same thing: Sit on the couch. Have a bag of chips or whatever other source of calories you come across. That’s what they’re programmed to do, and that’s what they will do over and over if you allow them to by leaving them in a consistent environment.
But if you introduce a change in behavior or resources, your cells are forced to become more resilient. Long ago, you might have needed resilience so that you could leap up from your sleep and make a sudden sprint away from a predator. Your body had to be strong enough and flexible enough to do that, or you wouldn’t survive. Today, things are a bit different: You can adjust the types of foods you eat and when you eat them and make your cells more resilient that way. Dietary exercise is exactly analogous to physical exercise. Long periods of inaction are terrible for your health; long periods of dietary consistency are similarly terrible for your metabolic health. It’s one more reason that rigid, CICO-style dieting is such a bad idea.
The more you mix things up and the more you reject consistency, the stronger and more flexible your cells will be. They will treat every day as a day when you are ready to leap into action. They will be ready to extract energy from any kind of food. They will no longer be trained to crave one particular snack or comfort food.
By reading this book, you have already started making a sincere effort to embrace inconsistency and free yourself from your cravings. The last thing you want to do now is imprison yourself with a new kind of craving, a craving for a certain style of fasting. You need to give yourself breaks and mix things up. You may reach the point where you think, “I don’t want to eat carbs. I don’t like how I feel when I eat carbs. Never again.” The correct response to that is “Shut up and eat some carbs from time to time.” Sure, you don’t want to eat processed sugar. I’m not encouraging you to gorge on cotton candy and Tootsie Rolls. But you can have a sweet potato or some rice. Or even some dairy-free ice cream. You’ll be okay. You’ll be more than okay, in fact, because you’ll be teaching your body to stay metabolically flexible.
You don’t want to be locked up by the fasting police any more than you want to be locked up by the calorie police. Fortunately, intermittent fasting is inherently flexible. As impossible as it might seem right now, you are capable of fasting for any length of time you attempt. Once you master the easy stages, you can try out the longer, more challenging ones. Over time, you will come to appreciate the different feelings and the different benefits you get from each of them. Always talk to your doctor before you embark on an extended fast, and stop a fast early if you start to feel really unwell, especially on the longer ones.
Believe it or not, we haven’t even gotten to one of the most sweeping benefits of intermittent fasting, which will liberate you from so
mething you probably aren’t even aware is holding you back—although it almost certainly is. Read on.
4
Fast for Long Life
Even before entering the cave for my vision quest, I felt like I’d arrived at a special place. From the outside, it looked as if the forces of nature had conspired to sculpt the perfect Instagram shot, with millions of years of geology and erosion coming together in this moment (except that Mother Nature probably hates Instagram). The gorgeous red-rock formation let sunlight in through a large, spherical portal in one wall that overlooked the valley below. There was a feather on the ground near the opening of the cave, lying there like a talisman. I instinctively picked it up, saw how it reflected the sunlight, and attached it to my backpack. At the end of the quest, I learned it was a bald eagle feather. I had no idea at the time—it’s actually illegal to possess a bald eagle feather, unless you’re from an indigenous tribe—but an eagle feather is believed to carry extra spiritual significance during a vision quest. To many of the local peoples, the eagle is a symbol of wisdom and courage, and an eagle feather can be used as a tool for healing. However it got there, I was grateful to have found it and gave it to Delilah on my return.
Yet even with all of those apparent synchronicities lining up the way you’d expect in a movie, a voice in my head nagged at me. A vision quest is not about bathing in glittering light and waving feathers around; it is about doing hard physical and spiritual work. I had come here to be hungry and alone and to forge myself into something stronger. I felt a nagging desire to go to a different cave, with no one around for miles. But apparently, that was not what fate had in store for me. The best I could do was to let things happen as they were going to happen and make the most of the situation by honoring Delilah’s instructions to remain in silence.
I chose a relatively flat, peaceful spot in the cave where I could sit alone(ish) for hours and then set up my sleeping bag, practicing complete silence (almost) the whole while. Despite my best efforts, I could hear my stomach and my brain grumbling about how hungry I was. I felt famished all day and night, but I did my best to confront and conquer those cravings. That first night, I fantasized about packing up my stuff and hiking to another cave that Delilah had mentioned was a mile away. There, I thought, I could truly face hunger by myself.
The next morning, when I dutifully turned on my phone to compose the text confirming that I was safe, it buzzed with a new incoming message from the shaman. “Pack up your stuff and come to the trailhead at 8am,” Delilah had texted. “I’m going to take you to another cave.” She hadn’t been kidding when she’d said she would be watching us remotely.
I hiked to the trailhead, and Delilah pulled up in her old pickup. Then she said something that blew my mind: “Last night you were thinking you really wanted to go to the First Woman cave, and that’s where you want to do your vision quest. So here I am to pick you up and take you there.”
According to tradition, true shamans can read your inner wants and desires, but I had never seen that ability in action. I hadn’t said a word to her, and I like to think I have a pretty good poker face. It was just one of several improbable-seeming things that happened during the vision quest. There are lots of hypotheses about intuitives and enough well-constructed scientific studies to hint that some people can accurately perceive other people’s thoughts. Maybe Delilah had noticed a tiny, subconscious hesitation in me while we’d been on our way to the original cave. Maybe she really could tune in to my energy from afar. The first step of the scientific method is to observe, so I can only tell you that that was what happened.
I refuse to fall into the trap that has held science back so often: the trap of facing evidence but then saying, “I don’t believe that could happen, therefore it didn’t happen.” If you start out insisting that something’s impossible, you will dismiss the evidence of it. In the process, you might miss something vital that could change the way you look at the world.
Call it freethinking or call it scientific method; either way, you’ll live a better life if you allow yourself to observe without prejudice or preconception. There’s a lot of evidence that your body won’t starve or even be harmed if you go a few days—or even weeks—without food. You may find that hard to believe. There’s an enormous food industry that doesn’t want you to believe that, and your body has been well trained not to believe it—just as my mind didn’t want to believe that the shaman could know what I had been dreaming about. But when you set aside your beliefs and open yourself up to new experiences, incredible things can happen.
EVOLVED TO EAT—BUT NOT LIKE THIS
The history of human evolution is also the history of food. Believe it or not, it’s the history of fasting, too. Our bodies and brains are inherently adapted to it.
The earliest fossil evidence of Homo sapiens pinpoints that our species originated roughly 300,000 years ago. Three meals a day were hardly the norm during that time. Our ancestors were opportunistic eaters, but above all they were hunters and gatherers, roaming the African plains in search of wild game:1 gazelles, antelope, wildebeests, zebras, and buffalos, with plants as backup. They traveled as clans, often walking miles at a time to find their prey. High speed was not as important as endurance or intelligence, because animals are inherently better sprinters. When an antelope or gazelle or whatever animal was finally caught, the feast was shared by all. There was rarely enough meat to last more than a few days.
When the food was exhausted, they hunted for more and subsisted on the few edible plants that would have been in season and not too toxic to eat. Until the next meal could be run down, everyone went hungry, yet no one died from going a few days without food. Fasting—either with no food or with a vanishingly few calories from plants—was simply a part of our ancestors’ lifestyles. They had no choice. This habit of eating and then fasting continued for not just decades or centuries or even a few millennia; humans have lived a lifestyle of feasting and fasting for almost 290,000 years. The fasting lifestyle is far more ancient than that, even; it’s the way of life for most large carnivores. Lions don’t sit down to three meals a day, for instance. When they get a good catch, they eat; then they may go three or four days before another major meal.
You may have heard about the “carnivore diet,” which combines a diet of only grass-fed meat with intermittent fasting. The good news about the carnivore diet is that it contains none of the plant toxins that spike hunger, which makes fasting really easy. Think of the carnivore diet as simply fasting from vegetables. If you’re like most people who try it, you’ll do it for a few weeks, love how you feel, and then eat a kryptonite-free salad. You’ll also gain a new understanding of how good you feel when you remove things that cause problems. Full fasting simply removes all foods that could be causing your bloat, brain fog, and metabolic problems. If you do it, follow the rules: eat only animals that are grass fed or wild caught, and eat the whole animal, including organs and connective tissues for collagen. As I said, intermittent fasting works with every diet under the sun.
One critical factor that distinguishes humans from other carnivores is that we use tools—especially fire. Modern genetic studies indicate that the invention of cooking was critically important in unlocking nutrition from foods that were too tough or too toxic to eat without being roasted over a flame. Cooking also makes it possible to consume more parts of an animal and to eat meat with less chewing. Scientists have found physical evidence of cooking hearths that are 500,000 years old; the Harvard anthropologist Richard Wrangham argues that our ancestors might have begun cooking nearly 2 million years ago.2 Either way, cooking is so ancient that it predates Homo sapiens. In retrospect, I wish I’d known that when I spent almost a year making myself sick on a raw vegan diet!
Our ability to get more energy and fat into the body allowed us to evolve bigger brains than those of other species. A bigger brain requires more electricity running through the body. Although your brain makes up just 2 percent of your weight, it consumes 15 to 20
percent of your metabolic energy. It takes a lot of electrons to power the 100 billion or so cells inside our mental supercomputer.
A big brain is the secret to our species’ evolutionary success, because it allowed our ancestors to think their way out of problems. It does the same thing for you, too—if you use it well. While some of our competitors evolved a thicker skull or bigger claws or a longer neck so they could eat leaves from tall trees, we got the big brain. Language, culture, science, technology, large-scale cooperation, and planning for the future are all by-products of this change. We humans are the dominant species of life on Earth today because of the size and complexity of our brain.
One of the big brain’s greatest contributions was that it allowed us to think our way out of starvation. Even after the introduction of spears, nets, and bows and arrows for hunting, humankind continued to fast. Not only did we thrive, but our brain thrived as well. The average brain size of early humans kept getting bigger and bigger, with much of the expansion happening in the section known as the prefrontal cortex. Over many tens of thousands of years, this lobe right behind our forehead developed into a powerhouse of decision making, planning, cognitive behavior, social interaction, and personality.