The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting

by Jason Fung

Have you ever been so busy at work or school that you simply forgot to eat breakfast and lunch? You were simply too focused on the task at hand to heed any of the numerous hunger cues. Your body just used some of the plentiful energy stored as body fat as fuel.

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.

We are wired for feast and famine, not feast, feast, feast.

eating—every meal should be enjoyed as a meal, not as something eaten while watching a movie. In

But in breaking habits, going cold turkey is not often successful.

If your habit is to eat munchies while watching television, simply stopping will make you feel like something is missing. Instead, replace that snacking habit with a habit of drinking a cup of herbal or green tea. Yes, this may seem weird at first, but you will feel a lot less like something is missing.

stimulating hunger as well as insulin production. I don’t recommend artificial sweeteners during fasting for this very reason.

following some simple rules will make hunger much easier to handle.

First, as mentioned above, artificial sweeteners can kick off the cephalic phase response, triggering hunger and insulin production, so I recommend avoiding them during a fast.

Second, try to physically remove yourself from all food stimuli during a fast. Cooking a meal or even just seeing and smelling food while fasting is almost unbearably difficult. This is not simply a matter of weak willpower. Our

You can also have a bowl of homemade bone broth at dinnertime on fasting days. It makes fasting easier in the long run.

One of our most important tips for fasting is to stay busy.

There’s no denying that you’ll experience hunger during fasting.

We often imagine that hunger will build and build until it is unbearable and we need to stuff ourselves with Krispy Kreme donuts. However, this is not the case at all.

The secret is to understand that hunger comes in waves. You just need to ride out the waves.

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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.

People weren’t hungry and actually felt “euphoric” during fourteen days of fasting. Some people felt so good during fasting that they wanted to continue past the fourteen days. In fact, the absence of hunger during extended fasting is a consistent finding throughout the scientific literature on fasting,

extended fasting gives people the chance to experience how hunger can disappear without eating as the body learns how to metabolize its own fat. The long fast rapidly acclimates their bodies to fasting. Once they get over the first one or two days, hunger starts to disappear and they become reassured that they are not overwhelmed by hunger.

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.

Most definitions of fasting allow noncaloric drinks only. This means that water, tea, and black coffee are all allowed during fasting,

The water-only fast is a traditional and classic variant—all other beverages and additives are not permitted during the fasting period. It’s important to note that this fast generally includes zero salt. Without salt, the body cannot hold onto water, and therefore there is some risk of dehydration. Some variants of the water-only fast allow you to drink salt water, although it can be difficult to get down. However, the body has a remarkable ability to retain salt when it is not readily available in the diet.

This means that as long as the water-only fast is limited in duration, your salt requirements will be fairly low, and salt deficiency shouldn’t be a problem.

“Green” juice fasting has recently surged in popularity. As you might guess from the name, this involves juicing green leafy vegetables, like spinach and kale. The resulting juice contains far less sugar than the juice of sweet fruits like oranges and apples. In addition, leafy vegetables contain little actual juice, so the leaves are often ground up and blended with the juice, which provides fiber and nutrients. Celery is often juiced in this mixture, too.

The “fat fast” is a newer variation of fasting. Relatively pure fats, such as coconut oil, cream, and butter, are allowed during this fast, so it, too, is not a true fast. Fat is normally not eaten in isolation—we rarely drink a cup of olive oil or eat a pat of butter by itself—but some people feel that eating fat this way helps reduce hunger and makes fasting much easier.

The popularity of “bulletproof coffee” has helped this trend. To make coffee “bulletproof,” you add fat in the form of coconut oil, medium-chain triglycerides (MCT oil), or butter from grass-fed cows. The high fat content of the coffee gives this drink a substantial number of calories (400 to 500 per cup, depending upon the recipe), so this would be more accu...

There are a number of purported benefits to the fat fast. Some claim that it helps weight loss as part of a ketogenic or very low carbohydrate diet, in which the body burns fat for energy. Others feel that the fat helps with mental clarity or that it helps kill cravings. While scientific proof of the effectiveness of the fat fast is currently scarce, anecdotes of success abound. In a “dry fast,” no fluids of any kind are allowed. Muslims practice this type of fasting during the daylight hours of the holy month of Ramadan. This combines fasting with mild dehydration. In my opinion, this makes fasting much more difficult than other types of fast, and I do not recommend this for medical reasons. The risk of complications is also much higher due to the accompanying dehydration.

Intensive Dietary Management Fasting: Best Practices We use fasting extensively in the Intensive Dietary Management (IDM) Program for weight loss and other metabolic disorders, such as type 2 diabetes and fatty liver disease.

You are always free to experiment and adjust, as there are no hard and fast rules. The IDM fast permits water, tea, and coffee.

natural flavors such as lemon juice, mint, cinnamon, or other spices are.

The IDM fast also allows homemade bone broth, which both makes fasting easier and may help prevent salt deficiency during longer fasts.

Water Be sure to stay well hydrated throughout your fast.

Aim to drink two liters of water and other fluids daily. As a good practice, start every day with eight ounces of cool water to ensure adequate hydration. Add a squeeze of lemon or lime to flavor the water, if you wish.

Alternatively, you can add orange slices, berries, or cucumber slices to a pitcher of water...

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Tea All types of tea are excellent choices, including green, black, oolong, and herbal. Green tea is an especially good choice during a fast: the catechins in green tea are believed to help suppress appetite. Teas can be blended together for variety and can be enjoyed hot or cold. Spices such as cinnamon or nutmeg add flavor.

Cinnamon tea and ginger tea have both been used for their reputed appetite-suppressing power. Mint tea and chamomile tea are often used for their soothing properties. Because herbal teas contain no caffeine, they can be enjoyed anytime during the day or night.

We often advise patients to go back to a classic water-only fast if they hit a stubborn weight plateau.

Coffee

is permitted during a fast. We also permit a small amount of cream or coconut oil to be added to coffee or tea.

Spices such as cinnamon or nutmeg may also be added,

Bone Broth Homemade bone broth, made from beef, pork, chicken, or fish bones, is a good choice for fasting days. Animal bones are simmered with other vegetables and seasonings for long periods of time, anywhere from eight to thirty-six hours—see here for a recipe. Vegetable broth is a suitable alternative, although bone broth contains more nutrients. All vegetables, herbs, and spices are great additions to bone broth,

We often advise people to add a good pinch of sea salt to their homemade bone broth. During longer fasts, it is possible to become deficient in salt since it is not taken with water, tea, or coffee, and salt deficiency can lead to dehydration. Sea salt also contains other trace minerals, such as potassium and magnesium, which may be particularly beneficial during fasting. (For shorter fasts, such as the twenty-four- and thirty-six-hour variety, it probably makes little difference.)

There is also a small amount of protein and some minerals (calcium and magnesium) in bone broth, so technically, any fast that allows broth is not a true fast. But many people have found that the broth makes a longer-duration fast much more bearable. The gelatin and protein contained in the broth help diminish hunger pangs, and there are numerous other health benefits ascribed to bone broth, including anti-inflammatory effects and benefits for bone and joint health.

obesity and type 2 diabetes—in today’s world of constant food abundance.

About ten thousand years ago, with the agricultural revolution and its greater reliability of food, we developed the habit of eating two or three times per day. But many early agricultural societies ate carbohydrate-based diets without problems with obesity. It seems to be a modern problem.

From these historical examples, we can see that it is certainly possible to eat meat and carbohydrates without the problem of diabesity in a society.