The Complete Guide to Fasting

Fasting is one of the most powerful and least utilized tools at our disposal. Learn what it is, what is isn’t, and how to do it effectively. It might just change your life.


“Fasting improves mental clarity and concentration, induces weight and body fat loss, lowers blood sugar levels, improves insulin sensitivity, increases energy, improves fat-burning, lowers blood cholesterol, prevents Alzheimer’s disease, extends life, reverses the aging process, and decreases inflammation.”

I’ve known about the spiritual benefits of fasting for a while now, but reading through The Complete Guide to Fasting was a great way to learn about the many health benefits. It’s a beautiful, well-written book with lots of charts, citations, and testimonials not included here. In addition, there’s a podcast called Fasting Talk where the authors discuss questions and concerns not addressed in the text. I found it to be a helpful supplemental resource.

What I liked most about The Complete Guide to Fasting: 1) it defines what fasting is and isn’t 2) it addresses common fasting myths and mistakes 3) it inspires readers to fast 4) it empowers readers to fast wisely and effectively 5) it promotes fasting as a way of life.

If you have any interest in this subject whatsoever, check out my notes below, and consider picking up a copy of the book. Fasting truly is one of the most powerful tools at our disposal but sadly, also one of the most neglected. The following information could change your life or the that of a loved one. Enjoy, and feel free to leave a comment or link below if you think it might add value to others.


  • The “calories in, calories out” (theory that you lose weight by consuming fewer calories than you expend) approach has been proven false. “Eat less, move more” doesn’t work either. Why? “The underlying cause of obesity turns out to be a hormonal, rather than a caloric, imbalance. Insulin is a fat-storage hormone. When we eat, insulin increases, signaling our body to store some of this food energy as fat for later use. It’s a natural and essential process that has helped humans survive famine for thousands of years, but excessively and persistently high insulin revels result inexorably in obesity. Understanding this leads naturally to a solution: if excessive insulin is causing obesity, then clearly the answer lies in reducing insulin. Both the ketogenic diet (a low-carb, moderate-protein, high-fat diet) and intermittent fasting are excellent methods of reducing high insulin levels.” 7
  • “Excessive insulin causes obesity, and excessive insulin causes insulin resistance, which is the disease known as type 2 diabetes. With that understanding, the problem with how doctors treat type 2 diabetes became clear: we were prescribing insulin to treat it, when excessive insulin was the problem in the first place….We doctors had been treating type 2 diabetes exactly wrong. With the proper treatment, it is a curable disease. Type 2 diabetes, like obesity, is a disease of too much insulin. The treatment is to lower insulin, not raise it. We were making things worse. We were fighting fire with gasoline.” 8-9
  • Dr. Fung realized that the key to lowering insulin levels had to do with reducing carbs.
  • Jimmy Moore on the relationship between a ketogenic diet and fasting: “Fasting and ketosis go together perfectly, like bacon and eggs. When you eat a low-carb, moderate-protein, high-fat diet – a ketogenic diet – it becomes much easier to fast. The carbohydrate restriction and protein moderation help to keep your blood sugar and insulin levels under control, and consuming adequate amounts of healthy saturated and monounsaturated fats keeps your hunger at bay. And here’s the key to why keto is so great for fasting: being in ketosis teaches your body to burn fat for fuel rather than sugar, and since that’s what your body has to do during fasting, if you’re already in ketosis, your body is already using fuel the way it’s supposed to. Think of it this way: You have at least 40,000 calories’ worth of fat on your body right now, but only 2,000 calories’ worth of sugar. If you’re a fat-burner, when you start fasting, your body simply continues to use fat as its primary fuel. If you’re a sugar-burner, though, your body burns those 2,000 calories of sugar until it’s all gone, and then it triggers hunger until it’s adapted to using fat. As a sugar-burner, you’ll feel the effects of hunger during a fast much earlier and more intensely. This is why going keto is a great first step for fasting, both IF and extended fasting.” 15-16 His book Keto Clarity is a great primer.
  • “Once my body made the switch from burning glucose to burning fat, the idea of eating breakfast, snack, lunch, snack, dinner, snack, midnight snack just seemed silly. Why would I want to eat that often when I wasn’t hungry?…Getting into ketosis will allow you to spontaneously fast for twelve to twenty-four hours. My own experience with fasting has been that it was difficult before I got into ketosis, and perfectly natural and easy afterward.” 20-21
  • “Most people don’t listen to what their body is telling them. Instead, they eat more out of habit, comfort, and boredom than anything else. This is critical to understand if you’re going to attempt to engage in fasting.” 22
  • “The notion that if you don’t eat, you’ll experience an increasing feeling of hunger the longer it lasts, is simply not true. In fact, I daresay that after fasting for a few days, you will actually feel more normal than perhaps you ever have before. And when you don’t think so much about what you’ll eat, when you’ll eat, where you’ll eat, and all the other social customs surrounding food, it frees you up to do other things. You’ll realize the urge and desire to eat is more mental than physical.” 24
  • Note: the more stress you experience while fasting, the harder it will be to maintain it.
  • The longer you fast (consecutive days), the more health benefits you receive. But listen to your body and eat when it’s clear that you need to.

Chapter 1: What is Fasting?

Fears – forget them
Advantages – so many
Schedule – whenever you need it
Therapeutic – for so many health concerns, like obesity, diabetes, cancer, and Alzheimer’s

  • Fasting vs. starvation: fasting is voluntary, starvation is not.
  • “Fasting has no standard duration – since it is merely the absence of eating, anytime that you are not eating, you are technically fasting. Consider the term breakfast. The word refers to the meal that ‘breaks your fast’ – which is done daily. The word itself implicitly acknowledges that fasting, far from being some sort of cruel and unusual punishment, is performed daily, even if only for a short duration. It is not something strange but a part of everyday life.” 39-40
  • Fasting is bad for business and nutrition authorities have misled us to believe that we must eat three meals a day, always be snacking, and never ever skip a meal.
  • “Fasting is effective, simple, flexible, practical, and virtually guaranteed to work. Ask a child how to lose weight, and she will probably say skip a few meals. So what’s the problem? Nobody makes money when you fast. Not Big Food. Not Big Pharma. Nobody wants you to find out the ancient secret to weight loss.” 41
  • “The average American eats five or six times per day.” 42
  • In general, when we eat, we increase insulin levels, which leads to storing more fat. When we fast, we decrease insulin levels, which leads to burning off sugar and body fat.
  • The longer you fast, the more your body moves from using glucose for energy to burning fat for energy. The body does not burn muscle.
  • “Periods of low food availability have always been a natural part of human history, and our body evolved mechanisms to adapt to this fact of Paleolithic life. Otherwise, we would not have survived as a species. There are no adverse health consequences to activating these protocols, except in the case of malnourishment. The body is not ‘shutting down’; it’s merely changing fuel sources, from food to our own fat.” 45-47
  • “All foods raise insulin to some degree. Refined carbohydrates tend to raise insulin the most and fatty foods the least, but insulin still goes up in both cases.” 47
  • The more you fast, the more insulin sensitive you become, which is a good thing. You want lower insulin levels. “The opposite of insulin sensitivity, high insulin resistance, is the root problem in type 2 diabetes and has also been linked to a number of diseases, including: heart disease, stroke, Alzheimer’s disease, high cholesterol, high blood pressure, abdominal obesity, nonalcoholic steatohepatitis (fatty liver disease), polycystic ovary syndrome, gout, atherosclerosis, gastroesophageal reflux disease, obstructive sleep apnea, cancer.” 47
  • “Most people expect that a period of fasting will leave them feeling tired and drained of energy. However, the vast majority of people experience the exact opposite: they feel energized and revitalized during fasting.” 49
  • As we age, our growth hormone levels drop, leading to more body fat, less muscle mass, and decreased bone density. Eating suppresses the release of growth hormone. “The most potent natural stimulus to growth hormone secretion is fasting. In one study, over a five-day fasting period, growth hormone secretion more than doubled.” 52
  • More and more athletes and bodybuilders are realizing the benefits of training in a fasted state.
  • “For optimal health, it is not enough to simply add fasting to your life. You must focus on healthy eating patterns.” Eat whole, unprocessed foods. Reduce sugars and refined grains (such as flour and corn products). Eat more natural fats (such as olive oil, nuts, avocados, coconut oil, wild salmon, meat, and dairy). Eat less artificial fats (found in shortening, fried foods, margarine, cookies and cakes, and corn/sunflower/canola oils). Balance feeding with fasting. 53-57

Chapter 2 – A Brief History of Fasting

  • “Fasting is the most time-honored and widespread healing tradition in the world. It has been practiced by virtually every culture and every religion on earth.” 64
  • Fasting advocates: Jesus, Muhammad, Hippocrates, Plutarch, the ancient Greeks, Paracelsus, Benjamin Franklin, Mark Twain.
  • “For most of human history, large amounts of food were not readily accessible all throughout the day. Intermittent fasting was likely a regular part of human evolution, and it’s possible our bodies – and brains – have come to expect periods of food scarcity. Because we are blessed with abundant food all year round in the twenty-first century, we now have to make a special effort to impose food scarcity upon ourselves for therapeutic purposes.” Amy Berger, 69

Chapter 3 – Busting the Myths of Fasting

  • Myth #1: fasting puts you in starvation mode. Truth: fasting puts you into optimal performance mode.
  • Myth #2: fasting makes you burn muscle. Truth: fasting makes you conserve muscle. If you want more muscle, exercise more.
  • Myth #3: fasting causes low blood sugar. Truth: fasting utilizes ketones to keep your blood sugar levels steady. “People who engage in fasting for religious or spiritual purposes often report feelings of extreme clear-headedness and physical and emotional well-being. Some even feel a sense of euphoria. They usually attribute this to achieving some kind of spiritual enlightenment, but the truth is much more down-to-heart and scientific than that: it’s the ketones! Ketones are a ‘superfood’ for the brain. When the body and brain are fueled primarily by fatty acids and ketones, respectively, the ‘brain fog,’ mood swings, and emotional instability that are caused by wild fluctuations in blood sugar become a thing of the past and clear thinking is the new normal.” Amy Berger, 79
  • Myth #4: fasting results in overeating. Truth: You may eat more calories the day after fasting, but you will still have a net deficit. Additionally, the more you fast, the more your appetite decreases.
  • Myth #5: fasting deprives the body of nutrients. Truth: fasting recycles nutrients in the body.
  • Myth: fasting is just crazy. Truth: fasting is healthy, smart, and doable.

Chapter 4: The Advantages of Fasting

  • “Fasting improves mental clarity and concentration, induces weight and body fat loss, lowers blood sugar levels, improves insulin sensitivity, increases energy, improves fat-burning, lowers blood cholesterol, prevents Alzheimer’s disease, extends life, reverses the aging process, and decreases inflammation.” 85
  • Diets often fail. Fasting offers many benefits over a traditional dieting approach: it’s simple, it’s free, it’s convenient, you can enjoy life’s little pleasures, it’s powerful, it’s flexible, and it works with any diet. 86-93

Chapter 5: Fasting for Weight Loss

  • The conventional “eat less, move more” approach popularized through shows like The Biggest Loser provide short-term weight loss, but over the long haul they have a 93 percent failure rate. Almost all of the contestants gain the weight back, as the rapid weight loss dramatically slows their metabolisms. One has gone on the record stating that they never have a reunion show because “we’re all fat again.” “This is the cruel hoax of the ‘eat less, move more’ strategy. It is cruel because all of our trusted health sources tell us it should work, and when it fails, we blame ourselves.” 104
  • The body has two fuel sources: sugar and fat. By eating fewer carbs or fasting completely, you can burn fat for fuel, which leads to sustainable weight loss.
  • High insulin levels tell your body to store fat instead of burning it, while also lowering your metabolism.
  • “The very low carb diet does remarkably well, providing you 71 percent of the benefits of fasting, without actual fasting. But sometimes low-carb just isn’t enough. A very low carb diet can reduce insulin by more than 50 percent, but you can go another 50 percent by fasting. That’s power.” 115
  • “The inability of most diets to reduce insulin resistance is exactly why they eventually result in weight regain. Fasting, on the other hand, introduces prolonged periods of low insulin levels, which breaks the cycle of high insulin and insulin resistance.” 118
  • “If you maintain a constant reduced-calorie diet, the body will quickly adapt to it. Energy expenditure (metabolism) declines to match the reduced intake. Weight plateaus, then is regained. This is not because you have stopped your diet but because your body has now adapted to it. To prevent your body from adapting to the new weight-loss strategy and maintain weight loss requires an intermittent strategy, not a constant one. This is a crucial difference. Restricting some foods all the time differs from restricting all foods some of the time. This is the difference between failure and success.” 118
  • Fasting works as well, if not better, than bariatric surgery, without the financial cost and potential negative side effects.

Chapter 6: Fasting for Type 2 Diabetes

  • “Type 1 diabetes is an autoimmune disease. For unknown reasons, the body’s own immune system attacks and destroys the insulin-producing cells in the pancreas, leading to a severe insulin deficiency. Type 2 diabetes is a dietary and lifestyle disease. In response to frequent high blood sugar, the body produces excessive insulin, which leads to insulin resistance.” 129-130
  • Type 2 diabetes rates have rapidly grown since 1980. Today, there are more Americans with prediabetes and diabetes than without.
  • On the powerful effects of fasting: “These results show that, rather than the chronic and progressive disease it’s often seen as, type 2 diabetes is a treatable and reversible condition.” 137
  • How type 2 diabetes is typically treated: “At first, the disease can be treated with a small dose of a single medication that stimulates the production of insulin. After a few years, this is no longer enough, so the dose is increased. After a few more years, a second, then a third medication is added, all aimed at increasing the production of insulin. Finally, insulin itself is prescribed in higher and higher doses. The progression of treatments is clearly not helping the underlying problem: the type 2 diabetes is just getting worse. If the core issue is that glucose is overfilling the cells, then the solution seems rather obvious: get all that glucose out of the cells! Pushing more in, as with insulin treatments, will only make things worse. So how do you get rid of excess glucose in the body?” 139
  • How type 2 diabetes should be treated: “There are really only two methods of getting the toxic glucose overload out of the body. First, you need to stop putting glucose into the body. You can achieve this with very low carbohydrate diets or ketogenic diets. Indeed, many people have reversed their diabetes by following such diets. Fasting also eliminates carbohydrates – and all other foods, for that matter. Second, your body needs to burn off the excess glucose. Fasting is again an obvious solution. Your body requires energy just to keep all the vital organs, such as the heart, lungs, liver, and kidneys, working. Your brain in particular requires substantial energy to function properly, even during sleep. During fasting, no new glucose is coming in, so your body has no choice but to use up the stored glucose. If you don’t eat, your blood sugar levels will come down. Once your blood sugar levels are consistently in the normal range, you will no longer be considered diabatic.” 139
  • If you’re on medication for type 2 diabetes, be sure to talk with your doctor before beginning a fasting regimen. You want to be monitoring your blood sugar levels so that they don’t get too low.

Chapter 7: Fasting for a Younger, Smarter You

  • Fasting boosts brain power. “Our ancient ancestors grew more alert and active when hungry so that they could find their next meal – and the same thing still happens to us. Animal studies show that fasting has remarkable promise as a therapeutic tool. Aging rats started on intermittent fasting regimens markedly improved their motor coordination, cognition, learning, and memory. Interestingly, there was even increased brain connectivity and new neuron growth from stem cells. A protein called brain-derived neurotrophic factor (BDNF), which supports the growth of neurons and is important for long-term memory, is believed to be responsible for some of these benefits. In animals, both fasting and exercise significantly increase the beneficial BDNF effects in several parts of the brain. Compared to normal mice, mice on an intermittent fasting regimen showed less age-related deterioration of neurons and fewer symptoms of Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease. In addition, insulin levels have an inverse correlation to memory – that is, the lower the insulin level, the more memory improves. On the flip side, a higher body mass index is linked to decline in mental abilities and decreased blood flow to those areas of the brain involved in attention, focus, reasoning, and more complex, abstract thought.” 148-150
  • In contrast, eating decreases brain power. “As the amount of blood going to the digestive system is increased to handle all the [food], less blood is available to go to the brain.” 148
  • Cells in our body are programmed to commit suicide at a certain age through a process called apoptosis. This sounds bad, but isn’t. It leads to renewed cell populations. Fasting stimulates autophagy, which is the process of our bodies removing the old, diseased, broken-down cells we no longer need. When apoptosis and autophagy don’t occur properly, diseases like cancer appear. “Increased levels of glucose, insulin, and proteins all turn off autophagy.” When we eat, we activate the mTOR pathway, which suppresses autophagy. When we fast, we keep the mTOR pathway dormant, and thus encourage autophagy to occur. 151-152
  • “Simply put, fasting cleanses the body of unhealthy or unnecessary cellular debris. This is the reason longer fasts were often called cleanses or detoxifications. At the same time, fasting also stimulates growth hormone, which signals the production of some new snazzy cell parts, giving our bodies a complete renovation. Since it triggers both the breakdown of old cellular parts and the creation of new ones, fasting may be considered one of the most potent anti-aging methods in existence.” 153

Chapter 8: Fasting for Heart Health

  • “A little starvation can really do more for the average sick man than can the best medicines and the best doctors.” Mark Twain
  • “The scientific community has long known that eating less cholesterol does not lower blood cholesterol. Our liver generates 80 percent of the cholesterol found in the blood, so eating less cholesterol makes little or no difference. By the same token, eating more cholesterol does not raise blood cholesterol significantly. If we eat less dietary cholesterol, our liver simply compensates by creating more, so the net effect is negligible. Furthermore, it’s not the cholesterol particle itself that’s cause for concern – remember, that’s identical in both LDL and HDL. It’s instead the lipoproteins carried along with the cholesterol particle that determine whether it’s good or bad.” 158-159
  • Numerous studies have proven that eating fat does not lead to high cholesterol. “Millions of people follow a low-fat, low-cholesterol diet because they think that it’s good for their heart, without realizing that these measures were long ago proven ineffective.” 162
  • Fasting is the best way to lower cholesterol – better than statins.

Chapter 9 – What You Need to Know About Hunger

  • Most people resist the idea of fasting because they are terrified of being hungry. “Somewhat surprisingly, practical experience with hundreds of patients shows that while they’re on an intermittent fasting regimen, they most often see their hunger diminish, not increase. They often report that despite their own expectations, they are eating less than half their usual amount of food on a daily basis, yet they feel completely full. For most people, this is the most pleasant surprise of fasting.” 167
  • Much of what we mistake for hunger is actually a conditioned response that we’ve learned over the years. We associate certain times, smells, sights, and cues with being hungry. “Hunger starts in the mind.” 169
  • On breaking associations and learning to eat when actually hungry: only eat at the table, replace snacking with coffee or tea, and avoid artificial sweeteners as they they trigger hunger and insulin production.
  • “For most people, the biggest obstacles to fasting are psychological, rather than physiological. In the modern industrialized world, we are accustomed to eating ‘round the clock. We eat when we’re happy, sad, bored, excited, stressed out, lonely, watching television, celebrating, and just about anything and everything else. In order to fast successfully, try to divorce yourself from the notion that you are ‘supposed to’ eat several times a day. It is okay – beneficial, in fact – to become reacquainted with feelings of hunger. In fact, it’s actually kind of nice to get reacquainted with the signals our bodies send us…when we finally allow them to come through. We are wired for feast and famine, not feast, feast, feast.” Amy Berger, 170
  • While fasting, dealing with hunger is easier when you remove yourself from food stimuli, have alternatives (coffee, tea, bone broth soup, etc.), and stay busy.
  • Think of hunger as a wave that comes and goes. It doesn’t keep building until it breaks you. “Hunger is not a continuously growing phenomenon. It will build up, peak, and then dissipate, and all you have to do is ignore it. It will certainly return, but knowing that it will pass once again gives you the power and confidence to handle it. This even applies to extended fasting periods. Hunger comes quite strongly during the first one or two days of fasting, generally peaking on day two. After that, the hunger just subsides and then goes away.” 173
  • “Hunger is not determined by not eating for a certain period of time. Rather, it is a hormonal signal. It does not come about simply because the stomach is empty. When you avoid natural stimuli to hunger, you help avoid that signal. Fasting helps to break all the conditioned stimuli and thus helps to reduce, not enhance, hunger.” 174

Chapter 10 – Who Should Not Fast?

  • People who shouldn’t pursue therapeutic fasting include: those who are severely malnourished and underweight, children under eighteen years of age, pregnant women, breastfeeding women. 179
  • People who should be cautious about therapeutic fasting include: those with gout, those taking medications (especially aspirin, metformin, iron and magnesium), those with type 1 or 2 diabetes, and people with gastroesophageal reflux disease. 179
  • Should women fast? “There is some persistent concern that women may not experience the same benefits of fasting as men. Nothing could be further from the truth. Virtually all studies on fasting confirm that both men and women benefit from fasting. Further, there is no particular difference in efficacy between the two sexes. If anything, women tend to do better.” 186 Women from a variety of religious traditions have been successfully fasting for thousands of years. And no, fasting does not negatively affect reproductive hormones.


Chapter 11 – Kinds of Fasts and Best Practices

  • There are a variety of fasting options out there. Water only fasting can work well, but watch out for salt dehydration over the long haul. Juice fasting is not technically a true fast, as you are consuming sugar and calories. Fat fasting allows for the use of foods like coconut oil, cream, and butter. It helps reduce feelings of hunger, keeps you on a ketogenic diet, and increases mental clarity. Bulletproof coffee is a popular part of fat fasting. It involves mixing coffee with MCT oil and grassfed butter or ghee.
  • “All types of fasts can have therapeutic benefit. The key to therapy is prolonged therapeutic ketosis (blood ketones in the range of 3-6mM), together with reduced blood glucose levels (3-4mM). Patients will need to use the Precision Xtra meter from Abbott to determine when they can enter the therapeutic zone. GKI ratios of 1.0 or below would best represent the therapeutic range.” Dr. Thomas Seyfried, 195
  • Dr. Fung does not recommend the fasting-mimicking diet due to the lack of evidence that it provides all the benefits of fasting and and its unnecessary complexity.
  • Water: both still and sparkling are fine. Aim for two liters of fluid a day. Can add lemon, lime, apple cider vinegar. Can infuse with orange slices, berries, or cucumber slices.
  • Tea: All types are excellent choices. Green tea is especially helpful due to appetite suppressing catechins. Can add milk or cream.
  • Coffee: both regular and decaffeinated are fine. Can add various fat sources such as coconut oil or butter.
  • Bone broth: Homemade is best. Add a pinch of nutrient rich salt. Avoid bouillon cubes (they contain artificial flavors and monosodium glutamate) and canned broths.

Chapter 12 – Intermittent Fasting

  • “The question of when to eat is as important as what to eat. It is precisely here that intermittent fasting may help us the most.” 199
  • Intermittent fasting is simply about picking a protocol for how long you want to fast and when you want to eat. There are a variety of options.
  • 12-hour fasts used to be the norm up until the 70’s. You would be done with dinner by 7 PM, and then break your fast (have breakfast) around 7 AM. Daily 12 hour fasts help keep insulin levels in check and fight obesity, but they are not enough to reverse weight gain.
  • 16-hour fasts (also called time restricted eating) are typically done by eating two meals within an 8 hour window (i.e. 11 am-7pm) and refraining from eating the rest of the time. This is a popular option for many people because most of the fasting period is spent sleeping, and a lot of people don’t feel hungry in the mornings anyway. You can lose weight on this protocol, but it’s slow going.
  • 20-hour fasts. Ori Hofmekler created this protocol in his 2002 book “The Warrior Diet.” Drawing inspiration from ancient tribes like the Spartans, this approach calls for eating only one meal in the evening during a four-hour window. It also emphasizes natural foods and high-intensity interval training.
  • On circadian rhythms: “Circadian rhythms are repetitive, predictable, cyclical changes in behaviors and hormones over twenty-four hours. Almost all our hormones, including growth hormone, cortisol, and parathyroid hormone, are secreted in a circadian rhythm. Circadian rhythms also help govern insulin, which affects weight gain, and ghrelin, which controls hunger – leading to practical implications for eating and weight loss.” 205
  • When we eat matters. Eating late at night spikes our insulin levels and leads to weight gain. Eating earlier in the day doesn’t have as dramatic of an effect.
  • Ghrelin, the hunger hormone, is lowest in the morning at 8 AM, and highest in the evening at 8 PM. So why eat breakfast if we’re not hungry for it and our bodies don’t need it? “Forcing ourselves to eat at a time when we are not hungry is not a winning strategy.” 208 But eating later in the evening isn’t wise either due to its adverse effects on insulin levels. So when is the best time to eat? Dr. Fung recommends eating the largest meal of the day “sometime between noon and 3:00 p.m., and only a small amount in the evening hours.” 208 This follows the timing of the traditional Mediterranean diet.

Chapter 13 – Longer Periods of Fasting

  • In order to reverse insulin resistance, we need longer fasting periods. Intermittent fasting is not enough.
  • If you are diabetic or are taking medications, you should definitely fast under the supervision of a medical professional. Your blood glucose levels could drop dangerously low, leading to hypoglycemia.
  • 24-hour fasts involve fasting from breakfast to breakfast, lunch to lunch, or dinner to dinner. These fasts have several advantages: they are short enough that you can still take any medications you’re on, they provide constant nutrition assuming you’re eating natural foods at meals, and they can work around family or job schedules.
  • The 5:2 Diet was popularized by Michael Mosley’s book The Fast Diet. It advises eating normally for five days and then fasting for two. To aid in compliance, men are advised to eat up to 600 calories a day while fasting, and women up to 500. It’s meant to be practiced indefinitely for the overall health benefits.
  • Alternate-day fasting involves fasting every other day and has been proven to be an effective means of weight loss.
  • 36-hour fasts involve not eating for an entire day. A typical fast might be from dinner one day until breakfast two days later. This type of fast can be especially helpful for patients with type 2 diabetes, as longer fasts are often required to undo much of the damage that has been done to their health. If you are diabetic, check with your doctor and be sure you are monitoring your blood sugar regularly.
  • 42-hour fasts typically combine going from a standard 16-hour fast straight into a 36-hour fast, totaling 42 hours. It is usually done two to three times a week.
  • Many of Dr. Fung’s patients have been cured of type 2 diabetes through diet changes and fasting protocols. “Type 2 diabetes is a dietary disease. As such, the only logical treatment is to change diet and lifestyle. If the problem stems from an excessive intake of carbohydrates, then reducing carbohydrates is the answer. If the problem stems from excessive weight, then successful weight loss with fasting is the answer. Once we fix the underlying issue, the disease reverses. However, we have been brainwashed to believe that type 2 diabetes and all its complications are inevitable. We have been deceived into believing that we can successfully treat a dietary disease with increasing doses of drugs. When the drugs fail to half the diabetes, we are told that the disease is chronic and progressive.” 223

Chapter 14 – Extended Fasting

  • Dr. Fung defines extended fasts as anything over 42 hours. They can produce dramatic benefits, and participants commonly report that feelings of hunger quickly fade after the second day and are replaced by feelings of well being and even euphoria. Many can go two weeks without any problems, but getting to that point can require practice and patience.
  • “Fasting has no upper limit. In the 1970’s, a twenty-seven-year-old Scottish man started fasting at a weight of 465 pounds. Over the next 382 days, he subsisted on only noncaloric fluids, a daily multivitamin, and various supplements, setting the world record for the longest fast. A physician monitored him during the fasting period and determined that there were no significant deleterious health effects. His body weight decreased from 465 pounds to 180 pounds. Even five years after his fast, he remained at 196 pounds. His blood sugar level decreased but remained well within the normal range, and he had no episodes of hypoglycemia.” 227
  • During extended fasts, the body shifts from burning glucose as fuel to burning ketones for fuel. This is a good thing, as ketones are a superior fuel source.
  • Electrolyte abnormalities are rare on extended fasts, but some supplementation may be helpful.
  • Bowel movements slow on extended fasts. This is normal and to be expected, as there is little to nothing going into the digestive system.
  • Seven to fourteen day fasts sound extreme but are relatively “easy” after making it through the first couple days. “A fourteen-day fast delivers seven times the benefit of a two-day fast but is only marginally more difficult.” Longer fasts are especially beneficial for patients who have severe type 2 diabetes.
  • Refeeding syndrome is extremely rare, but it is something to be aware of. It happens when your electrolytes get too low during your extended fast, leading your body to weaken when you start eating again. The people most at risk for this are those who are chronically malnourished or severely underweight. To be on the safe side, Dr. Fung recommends that his fasting patients drink homemade bone broth during their extended fasts, take a daily multivitamin, and maintain their normal exercise routine to minimize muscle loss.

Chapter 15 – Fasting Tips and FAQS

  • Top 9 fasting tips: 1) drink water 2) stay busy 3) drink coffee/tea 4) ride the hunger waves 5) don’t tell everyone you are fasting (those who don’t understand it may try to talk you out of it) 6) give yourself time to get used to fasting 7) follow a nutritious diet on non fasting days (high fat, moderate protein, low carb) 8) don’t binge when coming off your fasts 9) fit fasting into your life instead of trying to arrange your life around fasting. 236-237
  • Breaking your fast tends to go better when you drink water and have a small snack 30-60 minutes before your meal. It helps your body ease back into eating.
  • Dr. Fung’s top 5 natural appetite suppressants for use while fasting: water, green tea, cinnamon, coffee, chia seeds. 239-240
  • Other concerns: Dizziness: if you experience dizziness while fasting, you may need more salt and/or water. Headaches: headaches are common during the first few fasts and typically go away on their own. Salt/bone broth helps. Constipation: bowel movements should slow during fasts, but if you are having trouble after the fast has ended, consider adding more fiber, fruits, and vegetables to your diet. Heartburn: avoid large meals after a fast and drink sparkling water with lemon. Muscle cramps: typically caused by low magnesium. You can supplement, soak in Epsom salts, or use magnesium oil.
  • Answers to FAQs:
    • Fasting does not make you cranky, tired, confused, or forgetful.
    • Fasting can lead to more eating than usual, but even so, there is almost always an overall caloric net deficit.
    • Mineral water can help with a growling stomach during fasting.
    • Medications normally taken with food can be taken with leafy greens to maintain a fast.
    • If you have diabetes, consult with your doctor before beginning a fast.
    • You can exercise while fasting. You body will stop burning glycogen for energy and switch to burning fat. “Since your body is relying on your fat stores, there’s no shortage of energy during fasting, and you can and should do all your usual activities. There is no reason why exercise should stop during fasting.” Fasted exercise has significant benefits: “You can train harder due to increased adrenaline. You’ll recover from a workout and build muscle faster due to increased growth hormone. You’ll burn more fat due to increased fatty acid oxidation.” 245
  • On the natural rhythm of feasting and fasting: “There are times that you should eat a lot. There are other times that you should be eating almost nothing. That is the natural cycle of life.” Throughout history, people have always alternated between feasting and fasting. We should enjoy food when it’s time to eat, and make fasting a regular part of our lives. “What has happened in the past fifty years or so is that we have kept all the feasting but eliminated all the fasting. The normal balance has been perturbed, and obesity is the predictable outcome. If you feast, you must fast. That’s really all there is to it. It’s all a matter of balance.” 247-250
  • Recommended fasting fluids: 1) Water. Can add lemons, limes, fruit slices (don’t eat), vinegar, himalayan salt, chia, and ground flaxseed. 2) Coffee and Tea. Regular or decaf, hot or cold. Can add coconut oil, MCT oil, butter, ghee, heavy whipping cream, half and half, whole milk, and ground cinnamon. Try to limit added fat content to 1 tablespoon. Avoid sweeteners. 3) Homemade broth. Provides helpful electrolytes. Bone broth is superior to vegetable broth as it contains gelatin.

3 thoughts on “The Complete Guide to Fasting”

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