Intuitive Fasting: The Flexible Four-Week Intermittent Fasting Plan to Recharge You Metabolism and Renew Your Health

by Will Cole

autophagy—which is when your body cleans house and recycles dead and damaged cells and proteins—is triggered during periods of time without food. After about 8 to 10 hours without food, your body also enters something called ketosis, which is known for its beneficial effects on the brain and metabolism.

Unfortunately, with our high-sugar, high-carb, constant-snacking culture, it’s been a long time since many of us have burned any logs of firewood. In fact, many of us currently rely almost entirely on kindling (glucose) to fuel us and, as a result, our cells have lost their ability to quickly and efficiently switch from using sugar to using fat for fuel. In other words, we’ve lost our metabolic flexibility and, therefore, our ability to maintain consistent energy levels, brainpower, and appetites.

the mitochondria are the small energy centers in our cells. They have a few important functions, but above all else, they’re responsible for converting oxygen and nutrients into adenosine triphosphate (ATP), which is the main energy currency in the body. When you lose metabolic flexibility, your mitochondria lose their innate ability to efficiently switch between glucose and fat burning to maintain consistent energy levels—a

As you can guess, having trillions of cells inside us that behave like mini sugar addicts can make it impossible to connect to our body’s intuitive eating patterns. When your body is desperate for sugar because it can’t rely on burning fat for fuel, you’ll be hungry and craving something sweet, carby (or both!) every few hours no matter how much you eat. Those cravings will be so strong that they’ll crowd out your intuition.

Metabolic inflexibility breeds imbalanced inflammation in the body. Inflammation can be a nebulous term, so what is it exactly? It’s an essential manifestation of your immune system. Just like advancements in industry or the internet, inflammation is not inherently bad. It is merely subject to the Goldilocks principle: not too much, not too little, but just right, when we need it. When balanced, your body’s inflammatory response will save your life. Injuries and infections are healed with the power of balanced inflammation. Conversely, when your immune system is imbalanced, it is a forest fire burning in perpetuity, affecting every cell of your body. This is chronic inflammation.

The tricky part is that to your body, “sugar” isn’t just white table sugar. In fact, sugar can take the form of any simple carbohydrate, including pasta, bread, cereal, juice, desserts, candy, or even “natural” sweeteners like agave syrup or fruit juice. The more often you eat these foods, the more often your body has to go through the whole process of releasing insulin to usher the sugar into your cells. Your insulin will almost definitely have trouble keeping up with this onslaught of sugar, leaving you with excess sugar in your blood but no way to metabolize it.

By fasting and eating a low-carb, high-fat diet, you’re giving your insulin receptors a break from all that sugar. That way, you can banish insulin resistance and get back to being metabolically flexible.

cortisol release also causes our blood sugar to rise,

Chronic stress has also been connected to chronic inflammation and gut health issues. In fact, a study published in the Journal of Physiology and Pharmacology suggests that stress is linked to gastrointestinal conditions like IBS (irritable bowel syndrome), GERD (gastroesophageal reflux disease), and ulcers;

You can eat all the right foods and fast every night for 16 hours, but if you’re under extreme psychological stress on a daily basis, your body isn’t going to heal and become more metabolically flexible. You’ve got to show yourself some love, make yourself a priority, and take time to unwind.

when inflammation becomes chronic and sustained—owing to factors like a sedentary lifestyle, inflammatory foods, chemical exposure, and, yes, a lack of fasting and consuming too much sugar—it can lead to symptoms that range from mild weight gain and fatigue to chronic pain and autoimmune disease. Thus it will come as no surprise that identifying and correcting chronic inflammation is another key piece of the metabolic flexibility puzzle.

We must cut out those inflammatory foods and focus on eating an anti-inflammatory diet full of healthy fats, vegetables, and fiber in order to reestablish metabolic flexibility.

put your body into different healthy levels of nutritional ketosis, a natural metabolic state that kicks into gear when there’s not enough glucose (the kindling on the fire that I mentioned earlier) in your blood to use for energy. When there’s no sugar to burn for fuel, your body starts using stored sugar in the liver (glycogen) to release usable energy into the bloodstream. Once that runs out, your body starts to use stored fats instead (the sustainably burning firewood on the fire). This process creates ketones, a type of compound that your liver makes, in the body. When you have ketones circulating, your brain can use them as an alternative fuel source by converting them to energy through a process called beta-oxidation.

The first is by decreasing the carbs and sugars you take into your body so that there is less glucose in your blood to burn and your body turns to stored fat (this way of eating is known as the ketogenic diet). The second is by limiting eating drastically for an extended period of time (that is, fasting).

Even if you decide to reduce the amount of sugar in your diet, accomplishing it is not quite as simple as you think. Much of the sugar we consume is hidden, added where you’d least expect it, or disguised under a different name in the ingredients list of your favorite foods and snacks. In fact, sugar has countless euphemisms, so in order to avoid it, you’ll need to know them all and be able to recognize them at a moment’s glance. Even foods you’d never expect—like yogurt, ketchup, salad dressings, and pasta sauces—can be high in sugar. In order to reduce sugar, you need to check the nutrition labels of every food you buy and familiarize yourself with the different names it can be disguised under.

positive stress has been shown to be so beneficial that there’s even a scientific name for it: hormesis.

The historical origins of hormesis are quite fascinating. Mithradates VI (135–63 BC), the king of Pontus, a kingdom located in the modern-day eastern Black Sea region of Turkey, had suspected since he was a child that his mother would poison him to death. In an attempt to protect himself from his murderous mother, he would regularly ingest small doses of venom, believing this would defend him against all poisons. Since then, the system of administering nonlethal small doses of venom in an attempt to avert future poisoning has been termed Mithradatism.5 The sixteenth-century Swiss physician Paracelsus, known as “the father of toxicology,” is quoted as saying “All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison,” or “the dose makes the poison,” an adage reflecting the concept of hormesis. Today’s scientific literature further explores this concept.

Autophagy is important no matter our age, but it’s particularly critical as we get older, since aging hinders our ability to clean our old cells and proteins and all this debris can start to build up. Reductions in autophagy have been linked to a range of diseases. The authors of one study wrote that autophagy’s main job is to protect us from anything ranging from infections and cancer to neurodegeneration, accelerated aging, and heart disease.9

Ketosis, hormesis, autophagy, fighting chronic inflammation, and weight loss are the five key benefits of intermittent fasting. You may not be able to see all five of them with your own eyes, but, rest assured, if you’re fasting, they are happening behind the scenes, leading to concrete improvements in how your body and brain function. And even more important, they’re working hard to lead to measurable improvements in how you feel—in your energy level, cognition, pain level, physical appearance, mood, and even your disease status.

The problem is that the average ketogenic dieter cuts out sugar and carbs and often replaces them with pounds of processed meats, bacon, beef, cheese, and dairy from factory-farmed animals. These foods are often loaded with antibiotics and hormones, but many keto dieters believe they’re fine because they’re “low-carb, high-fat.”

Because of this hyperfocus on macronutrients over food quality, many people on the ketogenic diet begin to fear and avoid vegetables because of their carbohydrate content. This is a major issue I have with the conventional keto approach.

The Ketotarian Diet. The optimized plan in this book allows us to marry the benefits of a keto diet and the benefits of a mostly plant-based diet—and remove the cons entirely. The Ketotarian lifestyle was born out of my personal journey using food as medicine as well as my clinical experience. The Ketotarian way of eating brings together healthy plant-based fats, clean protein, and the rich, vibrant colors of nutrient-rich vegetables.

When it comes to macronutrients, you’ll be aiming for the following ratios: 60 to 75 percent of your calories should come from fat (but it can be more!). 15 to 30 percent of your calories should come from protein. 5 to 15 percent of your calories should come from carbohydrates. (Most people aim for somewhere between 20 and 55 grams of net carbs daily.)

But since we are all different, some people (especially women)—even after they are fat-adapted—feel better eating some more healthy carbs periodically or cyclically.

Clean Carb Cycling is a great tool to figure out where your carb sweet spot is and where you feel the best. This is important because eating too many carbs can interfere with your ketone production and blood sugar, but eating too few carbs can also backfire and interfere with your sex hormones, sleep, and weight loss goals.

Carbs from real foods like vegetables and avocados contain both insoluble and soluble fiber. Insoluble fiber such as cellulose and lignin can’t be absorbed by the body and has no effect on blood sugar and ketosis. On the other hand, soluble fiber such as galacto-oligosaccharides (GOS) and fructooligosaccharides (FOSs) are fermented by the gut microbiome into beneficial end products of bacterial fermentation called short-chain fatty acids (SCFAs): acetate, propionate, and butyrate. The concern in the mainstream ketogenic world is that soluble fiber can increase blood sugar levels, therefore negatively impacting ketosis.

However, studies have shown that soluble fiber can actually lower blood sugar levels.

In addition to all this science stuff, fiber can help with curbing cravings: ketosis + fiber from real food = craving-crushing magic. Win-win. Ketotarianism focuses on nutrient-dense real foods like vegetables, nuts, and seeds, which all contain carbs that are buffered and harnessed by whole-food fiber.

In short: When you are eating non-starchy vegetables, avocados, low-fructose fruits, nuts and seeds on the Ketotarian plan, count net carbs. If you eat processed, boxed foods (even the healthy ones) or any foods other than real whole food, count total carbohydrates.

You can’t heal a body you hate. You cannot shame or obsess your way into your wellness.

This allows for the natural production of ketone bodies—which we have already learned has protective and healing benefits for our brains, blood sugar, cardiovascular system, inflammation levels, and metabolism.

Ghrelin is secreted by your stomach and causes the physical sensations of hunger in your stomach. When ghrelin levels are high, you naturally eat more, store fat, and feel hungry.

Reset week is the initial calming of the noisy imbalance inside of you and gaining metabolic flexibility—the genesis of body intuition.

When you are fasting, you are giving your gut a much-needed rest, a gastrointestinal siesta. If you were in the habit of snacking throughout the day and eating late at night before the start of the plan, it’s almost definitely been a while since your digestion has had a significant rest.

The microbiome has its own circadian rhythm and is constantly cycling between different colonies of bacteria throughout the day. When we are sleeping, certain populations of bacteria increase. When we are awake and eat food, others may increase and flourish. This normal microbiome circadian cycle repeats every day but can be hurt when we are eating and snacking incessantly, especially if the food is unhealthy.

What you eat is especially important at your first meal of the day—when you break your fast. As a general rule, this meal needs to contain some healthy fats, like those found in olive oil, avocado, and nuts and seeds.

I suggest having them around dinnertime to avoid throwing off your metabolism during the day. By having your carbs in the evening, you also can capitalize on their fatiguing effect to help you wind down before bed. Some people also do well when they increase their carbs before or after a heavy workout.

These Clean Carb-Up days are a great option if you are a woman, if you’ve hit a weight loss plateau, or if you are struggling with some adrenal or thyroid issues. We’ll talk more about Clean-Carb Cycling during our Rebalance week (Week 4), but generally I do not suggest increasing carbohydrates to the higher end of these levels this early on for people who tend to have carb sensitivities, such as those with insulin resistance, diabetes, or inflammatory issues or those who have more than 10 pounds of weight to lose. If you are one of these people, you tend to be more carb sensitive, so giving your body more time in ketosis can aid in gaining metabolic flexibility faster. And to reiterate, no one needs to increase their carbohydrates if they feel great. When you increase your carbs, make sure you take note of how your energy levels, brain function, weight, mood, sleep, and digestion respond.

Be gentle with yourself. But before you move on to Week 3, you should make sure you have completed at least one 18-hour fast this week; the remaining days should be at least 14-hour fasting days.

Clearly, we need maintainable lifestyle interventions that effectively restore blood sugar health. Enter intermittent fasting, which is a fantastic tool for blood sugar control and can easily be implemented. When patients come in with blood sugar problems, I like to recommend intermittent fasting, because of its proven ability to reduce insulin resistance.8

you should know that fasting might be more difficult in the beginning if you have insulin resistance, and it may take longer for you to experience benefits.

too much inflammation and oxidative stress—both of which are ameliorated by fasting—are thought to be underlying causes of chronic fatigue.17 Therefore, don’t be surprised if you are shocked by how steady and energized you feel this week. You may start jumping out of bed without grogginess or stiffness and make it through the afternoon without a single yawn. In my own life and my patients‘ lives, this is one of the most practical, real-life benefits of fasting. Less fatigue means more energy to exercise, spend time with friends, or work on projects you’re passionate about—the list is endless. With increased energy levels often comes increased mood. As it turns out, fasting may also directly influence mood in a positive way. In fact, studies have shown that fasting can have antidepressant effects, which may be explained by a profound increase in neuronal autophagy (which is just autophagy of the brain cells) and an increase in serotonin, endorphins, and brain-derived neurotrophic factor (BDNF), a few major contributors to mood regulation.18, 19, 20

Both animal and human research has shown that intermittent fasting can improve risk factors for a wide range of chronic diseases, including autoimmune and inflammatory diseases, neurodegenerative diseases, chronic pain, and even cancer.

Millions of people’s immune systems are at war with their brains and nervous tissue, and this particular problem is drastically underdiagnosed. Autoimmune-inflammatory brain issues like multiple sclerosis, Parkinson’s, Alzheimer’s, and autism are affecting people now more than ever before in human history. So what gives? Well, just like diabetes or heart disease, all the conditions I just mentioned are intricately connected to our lifestyles and the negative effect our lifestyles have on our inflammation levels.

Also, as I have mentioned earlier, fasting increases the levels of brain-derived neurotrophic factor (BDNF) and supports neuroplasticity, your brain’s ability to make new neurons. BDNF plays a role in preventing neurodegenerative disease, but researchers are also studying it for the role it may have in managing chronic pain. This all makes sense, considering the fact that inflammation is a factor in both brain disease and chronic pain.

Antidepressants have been shown to decrease inflammation, so that may be an unknown mechanism by which they help improve mood.

For this final week, we’re turning our attention to our hormones. Why? Because one of the most important things to know about your body is that every part is connected, and your hormones are responsible for weaving every system together. They act as messengers, sending instructions to different areas of your body and regulating everything from your mood to your digestion to your metabolism—like a beautiful interconnected dance between every system of your body. You want your hormones to be happy because, at the end of the day, they’re often what makes the difference between your being happy or not. Hormones also play a key role in your ability to access your intuition about food, which is the second thing we’ll be focusing on this week.

This tailored approach allows you to use both the tools of fasting and a low-carb diet to help you reconnect with the way your body was supposed to feel. The Cellular Renewal fasts in Week 3 allowed you to put some sustainably burning firewood on the fire. Week 4 is all about putting some clean kindling on top to see what the perfect combination is. Metabolic flexibility is about balance and the ability to burn both glucose and fat when you want to.

The fact is, we are all different, and while some people do really well in long-term nutritional ketosis, others experience a greater benefit (and gain metabolic flexibility) when they strategically cycle out of ketosis now and then by upping their intake of healthy carbs. If you felt way better on your Clean Carb-Up days in Week 2, it may be because you simply need more carbs to balance things out in your body.

Carbs can be helpful macronutrients. As long as they’re eaten in a way that is healthy and that works for your biochemistry, they provide great fuel for your body and help many of your hormones and brain neurotransmitters function at optimal capacity.