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

by Jason Fung

that the advice to eat less and move more is simply wrong.

However, this model is known to be a complete fabrication.

To burn fat, two things must happen: you must burn through most of your stored glycogen, and insulin levels must drop low enough to release the fat stores.

The main issue is how to get access to the energy locked away in the fat.

Refined carbs and sugar in particular have the greatest effect on insulin, so a diet low in these is most

The answer we are looking for is, in a word, fasting.

So why can’t a successful weight-loss strategy be simply eliminating all carbohydrates instead of fasting? It’s simply a question of power.

Fasting, by restricting everything, keeps insulin lower. Fasting is simply more powerful.

Fasting is simply the most efficient and effective way to lower insulin levels. Notice, however, I did not say it was the easiest. But do you want a method that is easy, or a method that works?

During fasting, unlike during caloric reduction, metabolism stabilizes or even goes up to maintain normal energy levels. Adrenaline and growth hormone increase to maintain energy and muscle mass.

To prevent the 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 distinction. Restricting some foods all the time differs from restricting all foods some of the time. This is the difference between failure and success.

Ketone bodies produced during fat-burning fill that gap, and the brain becomes powered mostly on ketones, which supply up to 75 percent of its energy needs. This dramatically reduces the brain’s need for glucose, enabling adequate glucose production from glycerol.

This is a normal situation. This is the way our body is designed to work.

Perhaps the most common reason people give for their reluctance to fast is that it is too difficult.

autophagy (a cellular cleansing process), lipolysis (fat-burning), anti-aging effects, and neurological benefits. In other words, fasting can benefit your brain and help your body stay younger.

Despite popular belief, it’s not the tryptophan in the turkey causing that postprandial drowsiness—in fact, turkey has about the same amount of tryptophan as other poultry. It’s just the sheer amount of food. As the amount of blood going to the digestive system is increased to handle all that turkey and pie, less blood is available to go to the brain. About the only mental challenge we can handle after that enormous meal is sitting on the couch watching football.

derived neurotrophic factor (BDNF), which supports the

In animals, both fasting and exercise significantly increase the beneficial BDNF effects in several parts of the brain.

So fasting provides neurological benefits two ways: it decreases insulin and leads to consistent, maintained weight loss.

apoptosis,

apoptosis and

autophagy are both necessary to keep our bodies running well.

Increased levels of glucose, insulin, and proteins all turn off autophagy.

And it doesn’t take much. Even as little as

3 grams of the amino acid leucine can s...

In other words, the constant intake of food, such as snacking throughout the day, suppresses autophagy.

This is why the strongest stimulus to autophagy currently known is fasting, and why fasting alone, unique among diets, stimulates autophagy—simple caloric restriction or dieting isn’t enough.

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.

eating fat did not raise blood cholesterol.

Yet, almost universally, there is still an initial, severe resistance to the idea of even attempting to incorporate fasting into their lives. Why? One fear stands like a colossus above all others: hunger.

Studies of circadian rhythm confirm that for most people, hunger is very low first thing in the morning, even though it has been twelve to fourteen hours since the

Hunger, obviously, is not simply a reflection of the amount of food filling our stomach. Instead, hunger is partly a learned phenomenon.

We become hungry merely because of the time, not any true intrinsic hunger.

Conditioned responses, every one. The possibilities are endless.

Here’s the simplest way to break associations between food and anything else: Eat only at the table.

Try to avoid mindless eating—every meal should be enjoyed as a meal, not as something eaten while watching a movie.

Hunger is not a continuously growing phenomenon.

fasting protocol of 18-hour fasts for 5 days followed by 2 days water-only fasting. I also water-only fast for 10–18 consecutive days every other month.

The long fast rapidly acclimates their bodies to fasting.

It comes down to the fact that 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.

Fasting helps to break all the conditioned stimuli and thus helps to reduce, not enhance, hunger. Hunger is a state of mind, not a state of stomach.

It is more important to teach children about making proper food choices. Choosing to eat whole, unprocessed, natural foods is a good start.

There is some persistent concern that women may not experience the same benefits of fasting as men. Nothing could be further from the truth.

The water-only fast is a traditional and classic variant—all other beverages and additives are not permitted during the fasting period.

it is estimated that animal foods provided about two-thirds

Remember, you can always switch from one fasting regimen to the other. You are never locked in.

Hofmekler’s diet also emphasizes natural, unprocessed foods and high-intensity

intensity interval training, both of which I believe to be healthy practices.

The breakfast group lost far more weight than the dinner group. Why?

Folk wisdom, of course, also advises to avoid eating large meals in the evening. The reason offered usually is something along the lines of, “If you eat just before bed, you don’t get a chance to burn it off and it will turn to fat.