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

by Jason Fung

Atkins diet, promoting low-carb eating, was in full swing. It was everywhere. Some family members of mine tried it and were ecstatic with the results. However, like most conventionally trained physicians, I believed their arteries would eventually pay the price. I, along with

thousands of other physicians, had been taught and certainly believed that low-carbohydrate diets were simply a fad and the low-fat diet would prove to be the best.

the low-carb diet was significantly better for weight loss than the low-fat diet.

I was still steeped in the conventional “calories in, calories out

Logically, accepting that the studies were correct meant the CICO approach had to be wrong. Much as I tried to deny it, there was no saving the CICO hypothesis. It was dead wrong. And if the CICO hypothesis was wrong, then what was right? What caused weight gain? What was the etiology—the underlying cause—of obesity?

too many calories is the problem,

then the solution is eating fewer calories and burning

more through an increase i...

But there’s an obvious problem. “Eat less, move more” has been done to death over the past fifty...

The underlying cause of obesity turns out to be a hormonal, rather than a caloric, imbalance.

Both the ketogenic diet (a low-carb, moderate-protein, high-fat diet) and intermittent fasting are

excellent methods of reducing high insulin levels.

an annual seven- to ten-day water fast could be a useful tool for preventing cancer.

“fasting allows you to reclaim your hunger for what it is [so] it no longer dictates what you put in your mouth.

When you eat a low-carb, moderate-protein, high-fat diet—a ketogenic diet—it becomes much easier to fast. The

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.

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

distilled water only and nothing else.

By eating a low-carb, moderate-protein, high-fat diet, I was able to switch my body from primarily burning glucose for fuel to burning fat.

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.

We simply aren’t meant to be eating as much

or as often as we do in modern culture, and getting into ketosis by consuming real, whole foods on a diet that is low-carb, moderate-protein, and high-fat, with adequate calories, will allow you to spontaneously fast for twelve to twenty-four hours.

That’s the bottom line to remember—once you’re accustomed to fasting, it happens very naturally and shouldn’t be associated with much hunger or discomfort after the first few times.

In other words, most likely I lost not muscle but rather fat around my internal organs—a very good thing!

The fact is, I didn’t lose any muscle during my twenty-eight days of fasting, and that’s pretty remarkable!

There is no correlation whatsoever between constant eating and good health.

Fat triggers a far smaller insulin effect, but it’s rarely eaten alone.

A therapeutic fast of 382 days was maintained with only a multivitamin with no harmful effects on health. In fact, this man felt terrific during this entire period.

However, the vast majority of people experience the exact opposite: they feel energized and revitalized during fasting.

studies show that after a four-day fast, resting energy expenditure increased by 12 percent. Rather than slowing the metabolism, fasting revs it up.

However, exogenous growth hormone—that is, growth hormone that isn’t made by your own body—carries the risk of unwanted side effects.

The most potent natural stimulus to growth hormone secretion is fasting.

Interestingly, very low-calorie diets are not able to provoke the same growth hormone response.

For optimal health, it is not enough to simply add fasting to your life. You must also focus on healthy eating patterns.

high insulin levels are the root cause of all the diseases of metabolic syndrome,

During processing, the natural balance of macronutrients, fiber, and micronutrients is completely disrupted.

If it has a nutrition label, it should be avoided.

The true secret to healthy eating is this: Just eat real food.

it’s most important to avoid sugars and refined grains, such as flour and corn products.

And more and more evidence is showing that naturally occurring saturated fats, such as those found in meat and dairy, are also not harmful to our health.

In fact, fasting is one of the most potent stimuli for growth hormone secretion, and increased growth hormone helps maintain lean body mass.

They usually attribute this to achieving some kind of spiritual enlightenment, but the truth is much more down-to-earth and scientific than that: it’s the ketones! Ketones are a “superfood” for the brain.

For longer fasts, it is a good idea to take a general multivitamin. The longest fast recorded lasted 382 days, and a simple multivitamin prevented any vitamin deficiencies.

Since refined carbohydrates are a prime contributor to high insulin levels, the natural place to start with my patients was a low-carbohydrate diet.

the best diet would emphasize whole, unprocessed foods. It would be low in refined carbohydrates and high in natural fats with a moderate amount of protein.

Yes!

Now, I am not saying that you should eat dessert every single day. However, fasting restores the ability to occasionally enjoy that dessert by balancing out the feast. It is, after all, the cycle of life. Feasts follow fasts. Fasts follow feasts.

Fasting is really about balance

That's what I am talking about!

The quickest and most efficient way to lower insulin and insulin resistance is fasting.

Long-term dieting is an exercise in futility. All diets—whether the Mediterranean diet, the Atkins diet, or even the old-fashioned low-fat, low-calorie diet—seem to produce weight loss in the short term.

In other words, eventually, all diets fail.