by Dave Asprey
Ketones not only provide energy, they also make you more alert. I recently met with Satchidananda Panda, an expert on the body’s internal circadian rhythm clock, as he was working at the Salk Institute in La Jolla, California. As we walked down the central outdoor path at the institute, I could see why its architect created it to be “worthy of a visit by Picasso.” Even so, Satchin’s research is far more epic than the buildings. He’s found that ketones act as miniature alarm bells, rousing the brain cells that regulate the circadian rhythm and instructing the body to switch into an active, awake state.11 A small rise in ketones from fasting provides a burst of energy, which likely evolved to help you have a more successful hunt. It is an evolutionary gift from our ancestors, and you can turn on that burst of energy at will by using ketosis. Ketones in the morning, when you “break fast,” flip the switch on that energy for many hours.
C8 MCT oil is converted directly into ketones in the body, and coffee contains caffeine, which doubles your ketone production, according to a study by Canadian researchers.12 An elevated ketone level stimulates production of cholecystokinin, or CCK (the “stop eating” hormone) and cuts off production of another troublemaking hormone, ghrelin, which is produced in the stomach and small intestine. Biologists have nicknamed ghrelin the “hunger hormone” because it stimulates the desire to eat and activates the hypothalamus, a part of the brain that helps regulate appetite. It’s all part of the many overlapping, synergistic benefits of intermittent fasting.
These days, people often use a term I created a decade ago, biohacking, to describe fine-tuning your control of your body. That word makes it sound like a futuristic idea, which is only half true. Adjusting the way you eat to promote healing and wellness is an ancient practice—as ancient as life itself. The biological mechanisms for self-cleansing and rejuvenation have been built into us by billions of years of evolution, as have our instinctive responses to food. What’s new is that we can study the processes happening inside us at the molecular level; understand exactly why they are happening; and make deliberate choices to enlist those processes for maximum benefit with minimum discomfort.
FAST YOUR WAY
Depending on your current lifestyle, fasting might put your body through some significant changes. I therefore recommend that you start gently, which will minimize any initial discomfort and bring you more quickly to the joyous stages of fasting. You might start your day with coffee and a teaspoon or two of MCT oil. Hey, maybe you’re a big guy and you need more. You read this and think, “I’m 400 pounds, and there’s no way I’m going to survive on a couple tiny teaspoons of MCT.” Fine, use a tablespoon or more if your body tells you it needs more. You can even try switching to black coffee some days and see if you feel better or more alert. The specifications are up to you; what matters is that your biological systems are going to read the chemistry in your blood and determine that are you’re fasting even though you’re drinking a cup of coffee and don’t feel hungry.
It’s not just a fake-out. Contrary to what water-drinking pedantic fasters might suggest, you’re really fasting! You’re fasting because you aren’t eating any protein, so your body doesn’t need to use up any of its protein-digesting molecules (proteases) to break down food, and your insulin level doesn’t change. Instead, your body is devoting all of those resources to folding new proteins, cleaning up old cells, and repairing cellular damage—that is, it’s busy doing autophagy. Though you think you’re eating, your body thinks it’s fasting. All the right healing mechanisms are already there in your body; all you have to do is set them free to do their job unhindered.
Maybe the idea of replacing breakfast with a coffee concoction just doesn’t sound great to you. At least it’s far better tasting than a kale smoothie, which doesn’t taste good and isn’t good for you, either. There’s still a way to get the benefits of fasting: try a protein fast. Protein fasting means that one day a week, or longer, you eat less than 15 grams of protein from all sources, including vegetables. You can enjoy some fat, have some vegetables (just not high-protein vegetables such as lima beans and spinach), and eat almost anything that’s not high protein or straight sugar. Do that once a week, and you’re going to get many of the benefits of fasting without fasting, because a low protein intake lowers insulin and a critical metabolic protein called mTOR,13 exactly as fasting does. As I said: fasting is going without, but going without doesn’t always mean going without everything. You get to pick.
This kind of flexibility is sure to piss off the fasting purists. There are some people out there who love ironclad rules for how to live your life. I’m sure you’ve met a lot of them or at least seen their comments online. There are people who genuinely believe that they aren’t dieting or fasting correctly unless they’re suffering. That’s not my fast. I’m going to do what works, even if there are no studies yet showing why it works. I’ve used protein fasting for more than a decade, and I’ve spoken to many other people who’ve adopted it since I set out the basic principles in my book The Bulletproof Diet. So I can tell you: protein fasts work; simple as that.
If you can’t live without protein, you can try another kind of fasting: don’t eat carbs; ingest only fat and protein. There’s a name for that kind of fasting, and it’s all the rage: the keto diet. What if we add onto that? How about avoiding inflammatory proteins and inflammatory fats? Your diet may be chock full of inflammatory fats without your knowing it, since Big Food doesn’t tell you (and often doesn’t even know) which fats are harmful to you. Many common oils—including canola, corn, peanut, and soybean—are inflammatory omega-6 fats. You may be amazed how much better you’ll feel if you get rid of them. Plus, gluten and casein (milk protein) are inflammatory, and you won’t get results if those are your protein sources. All of these different approaches fall within the scope of Bulletproof Intermittent Fasting. We’ll discuss even more ways to fast in chapter 10.
Close your eyes for a moment, and picture what you imagined a fast would look or feel like before you started reading this book. Perhaps you were picturing a health fanatic exerting some sort of Herculean effort to refuse all food—and yourself suffering in an attempt to emulate that effort. I don’t blame you; there are plenty of books, magazines, and infomercials promoting this stereotype. Now close your eyes again, grab hold of those images, and erase them from your mind. I want to prepare you for embracing a fasting method designed around selectively and surgically going without. I want you to learn how to fast in any way that works for you—not just this week or this month or even this year but for the rest of your life. Fasting has to be sustainable to be meaningful, and being sustainable means that you make the least possible effort and feel the least possible pain.
You read that right: the least possible effort; the least possible pain.
Your decision to travel down this path will lead you into a very different world. You’re going to unleash the power of all of those biological mechanisms in your cells. They’ve been honed by millions of years of natural selection to take care of you. You just have to learn how to activate them correctly—to make them work for you, rather than the other way around.
Unlike other methods of fasting or dieting, I promise that when you fast this way you won’t be hungry. You won’t be cold, you won’t be tired, you won’t have brain fog, you won’t be hangry, you won’t be hypogly-bitchy (that’s the foul mood that often strikes when you have low blood sugar, or hypoglycemia). The ketones and metabolites and NAD+ and leptin and all of the other biochemicals you are enlisting will take care of you. You’ll feel focused at work all day and come home in a good mood. Your brain will feel sharper than ever and you’ll feel younger, with a gut that will repair itself. You’ll lose weight, too, even though that’s not the primary goal of intermittent fasting. What matters the most is that you’ll have the energy and clarity to pursue whatever it is that you want in life.
Your entry into the world of fasting begins the same as my entry into the shaman’s cave: you push ahead, take the f
irst step, then another. Put it to your own personal test. Try going for twenty-four hours on just water and see how you like that. Or maybe try experimenting with just water and then black coffee in the morning. Don’t eat anything on the second day until two in the afternoon and see how you like that. If you’re metabolically fit, your body digests fat well, and you’re used to fasting, it’s not going to matter. You’ll be just fine. But if you’re new to this, and you are like I used to be in my twenties, you’re going to feel like crap on just water or black coffee. Anxiety. Anger. Brain fog. That’s fine, too. It will get easier with time, or you can explore a whole range of intermittent fasting biohacks here that make it easier now. Experimentation is part of the fun, as you learn more about yourself. Again, suffering is not the goal.
There’s another hack you should know in order to fast like a boss. Sometimes you’ll take on a fast because there’s something bad going on in your gut. You know what I’m talking about: there’s rumbling, there are things no one wants to smell, and, well, you have a most inconvenient problem. The best solution is to not have anything inside your gut, which will suppress the bad behavior of your internal bacteria. When your gut bacteria don’t have any food, they freak out. In fact, they freak out so badly that they make something called FIAF—fasting induced adipose factor—which they use to sneakily tell your body to burn extra fat for energy, so the bacteria’s home (your gut) will stay alive longer. This works to your advantage, except that when gut bacteria get stressed, they also increase the production of a group of compounds called lipopolysaccharides. And let me tell you, when lipopolysaccharides come across your gut barrier, you are not going to like how you feel. They are well-known toxins. This is one of the reasons that when you first go into ketosis or first start fasting, you typically get what is known as “keto flu.”
One of the simplest hacks is adding a little activated charcoal to your fasting protocol. It binds directly to those lipopolysaccharide molecules, which is probably why ingestion of activated charcoal extends animal (and likely human) life span,14 but it doesn’t stop the good guy, FIAF, according to current research. Taking activated charcoal is also a simple way to help soothe the gut pain and many other discomforts that might occur when you first start fasting. I’ve been sharing the benefits of activated charcoal for years, but it’s hardly original with me; it was a part of indigenous American dietary traditions for unknown ages before Europeans arrived. Various Native American peoples knew that activated charcoal soaks up toxins in the gut and tames the production of intestinal gas. I found it in the jungles of Peru and in Nepal; it’s one of the earliest remedies known to humans. It works even when you’re not fasting but are just experiencing a stomachache.
While you are taking control of your internal biology through fasting, you also want to take control of your microbiome. Collectively, there are about as many bacteria in your body as there are human cells. According to the latest estimate coming out of the Weizmann Institute of Science in Israel, there are about 30 trillion of them living inside you!15 They are much more than microbial hitchhikers; they are an integral part of your internal ecosystem, to the extent that some medical scientists now call the microbiome a “supporting organ.” Your gut bacteria help break down complex carbohydrates, neutralize toxic compounds, aid in the synthesis of certain amino acids and vitamins (including B-complex vitamins), and produce compounds that influence your metabolism.
The vast majority of your microbiome should be helpful or at least benign, but there are some bad actors mixed in there, too. In a well-balanced microbiome, the good bacteria help keep the harmful ones in check. For all these reasons, you want to take antibiotics only as a last resort. Many antibiotic drugs are “broad spectrum,” meaning that they slaughter both good and bad bacteria indiscriminately. It’s like burning down an old forest, full of a rich diversity of wildlife, to get rid of a patch of poison ivy. Your microbiome will bounce back once you finish your course of medication, but it probably won’t be quite the same as before—and there’s a chance that you will have created more opportunity for the bad bacteria by clearing out so many of the good ones.
When you’re fasting, you need to keep the health of your microbiome in mind. This is a fairly new concept. Although people have long understood the importance of maintaining a healthy gut, it’s only in the past decade or so that scientists have begun to decode16 the vast number of intricate, intimate biochemical interactions between you and your microbes. With that knowledge now in hand, we can begin to expand the concept of biohacking to include hacking your microbiome during fasting.
Some ecosystems require an occasional drought or fire to clear out old brush and allow new seeds to sprout. Your gut biome will almost certainly benefit from an occasional longer fast for the same reasons, and fasting can eliminate bad bacteria in the gut. The problem is that excessive fasting can also knock out good gut bacteria, and most of us don’t get enough fiber to feed the good guys anyway.
To maintain healthy gut bacteria levels with or without a fast, you can take various types of prebiotic fiber. These are marvelously useful substances that are compatible with most kinds of fasts. Soluble fiber attracts water in your stomach and intestines and turns into a gel, which slows the digestive process. Common sources of dietary fiber include oats, bran, nuts, and seeds, none of which are fasting compatible. Instead, you can opt for a blend of acacia gum, guar gum, and larch arabinogalactan. These scary-sounding things are just plant-based tree saps that you can buy as flavorless powders that blend well into coffee or any other liquid.
Technically, these prebiotic fibers are carbohydrates, but the fibers are a tough form of carbohydrate that cannot be digested and burned as carbs by your body. Instead, they become a food source for your microbiome, which breaks the fibers into ketogenic fats. Those fats act to switch off the sensation of hunger during your fast, while the bulking properties of the fiber make you feel full. Pretty clever biohack, right?
When you take prebiotic fibers, you get none of the carbohydrate effects that you would normally get, but your levels of good bacteria explode. These fibers are shown to increase your life span and reduce all-cause mortality. Prebiotic fibers moderate the changes in your blood sugar, adding to the insulin-regulating benefits of fasting. Here’s the kicker: these fibers are also associated with weight loss. If you take soluble fiber while you fast, you don’t get a complete gut rest, but you do get all the energy benefits and all the longevity benefits, and you don’t feel the pain of the fast. It’s almost impossible to be hungry after mixing 20 grams of prebiotic fiber and a little MCT into a cup of black coffee.
Most ancient fasting practices also involve drinking at least a little bit of tea. As you know, I prefer coffee in my modern fast. Why? Well, the amount of caffeine in two small cups of coffee will double your ketone production, and ketones are what you want when you’re fasting. Coffee and fasting go together like motherhood and apple pie or teenagers and cell phones. I strongly recommend coffee in the morning (and not just because I created Bulletproof Coffee!). It really does make a difference. If you’re not a particular fan of drinking coffee, think of it as the fasting equivalent of eating kale. You may not like the taste of kale, but you eat it because you’ve been programmed to believe it’s such a healthy food. Look at coffee as a superfood for your fast, another part of the tool kit that allows you to direct the way your biology works.
You’ve now learned about three remarkable and remarkably simple components of an effective fast: coffee, MCT oil, and soluble fiber. All of them will enable you to turn off hunger, take in calories, and still maintain your fast. Maybe you didn’t believe me before when I told you that fasting is not about suffering? I hope you’re starting to believe now.
You may hear people say that if you’re consuming caffeine, fats, and fiber (even small amounts), you are not technically fasting. Generally speaking, those people are either purists trying to justify their own pain, or they are trying to sell you something. Over the ye
ars, hundreds of thousands of people have looked into my work on intermittent fasting—everyone from research scientists to the engaged readers of my books and blog. They can all testify that it works. I can also confirm that personally, as someone who has lost weight and kept it off and who has routinely practiced intermittent fasting for years. Best of all, you don’t have to take any of this on faith. You can run the experiment on yourself and quickly discover firsthand that this approach really works.
If you’re into self-flagellation, feel free to grit out your fast without these biohacks. Just be prepared to endure the kind of needless pain that will get in the way of the rest of your life as your metabolism becomes stronger. Think about running a business, finding a new job, or tending to a kid hanging off each arm. Do you want to face those challenges feeling hungry, weak, and irritable as your body adapts? Or do you want to come at them from a place of strength, peace, and vigor?
When you fast this way, you fast your way. The biochemical systems in your body determine how your body responds to fasting, but you determine how to activate them. You are in control of what fasting does to you. The most important thing fasting does to you is that it puts you in charge of your life.
What Does Fasting Do for You?
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Makes your body burn fat (ketosis)
Helps your gut heal itself
Provokes the body’s self-cleaning (autophagy) and detoxification processes
Reduces your risk of almost every chronic disease
Causes your body to produce more stem cells
Reduces your risk of type 2 diabetes by improving insulin sensitivity