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

by Jason Fung

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

Even more stunning was that all the

important risk factors for cardiovascular disease—including cholesterol, blood sugar level, and blood pressure—were also ...

Insulin is a fat-storage hormone.

When we eat, insulin increases,

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.

If you drink excessive alcohol, your body will develop resistance,

you use prescription sleep medications such as benzodiazepines, your body will develop resistance.

excessive insulin causes insulin resistance, which is the disease known as type 2 diabetes.

As patients took insulin, they gained weight, and when they did, their type 2 diabetes got worse, demanding more insulin. And the cycle repeated: they took more insulin, they gained more

weight,

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.

Jimmy Moore.

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

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’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

The first few days I lost about a pound a day, and then on days 4 to 7 I lost several pounds. While I wasn’t doing

hadn’t consumed anything in many days, so what was coming out? It reminded me that there’s a lot more waste in the body than we even realize, and doing this fast may have helped clean a good bit of that out.

something incredible happened once I got past the second day: fasting became surprisingly simple! It was almost too easy to just not eat. 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.

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

I had certainly read a ton on the anti-aging benefits of fasting,

I was forced into a 36-hour fast. I found myself completely energetic and

clear-headed. Based

also noticed that I didn’t lose mass or strength, which was key for me.

it has enormous health benefits.

lose weight? Of course.

Fasting is effective, simple, flexible, practical, and virtually guaranteed to work.

Nobody makes money when you fast. Not Big Food. Not Big Pharma. Nobody wants you to find out the ancient secret of weight loss.

I think the hardest thing about fasting is deciding to do it.

but once I start, that block dissolves and it becomes easier.

When we eat, we ingest more food energy than we can immediately use. Some of this energy needs to be stored away for later.

The key hormone involved in both the storage and use of food energy is insulin, which rises during meals. Both carbohydrates and protein stimulate insulin. Fat triggers a far smaller insulin effect, but it’s rarely eaten alone.

Insulin has two major functions. First, it allows the body to immediately start using food energy. Carbohydrates are absorbed and rapidly turned ...

Insulin allows glucose to enter directly into most cells of the body, which use it for energy. Proteins are b...

absorbed, and excess amino acids may also be turned into glucose. Protein does not raise blood glucose, but it can raise insulin levels. The effect is variable, and it surprises many people to learn that some proteins can stimula...

are directly absorbed as fat and have minimal ef...

Second, insulin helps store the excess energy. There are two ways to store the energy. Glucose molecules can be linked into long chains called glycogen and then stored in the liver. There is, however, a limit to the amount of glycogen that can be stored away. Once this limit is reached, the body starts to turn glucose int...

This newly created fat can be stored in the liver or in fat deposits in the body. While turning glucose into fat is a more complicated process than storing it as glycogen, there is ...

when we fast. Insulin levels drop, signaling the body to start burning stored energy. Glycogen (the glucose that’s stored in the liver) is the most easily accessible energy source, and the liver stores enough to provide energy for twenty-four hours or so. After that, the body starts to break down stored body fat for energy.

six to twenty-four hours after beginning fasting): At this point, blood sugar and insulin levels begin to fall. To supply energy, the liver starts to break down glycogen, releasing glucose. Glycogen stores last for approximately twenty-four to thirty-six hours.

Fat is simply the body’s stored food energy. In times of low food availability, stored food is naturally released to fill the void. The body does not “burn muscle” in an effort to feed itself until all the fat stores are used up. (More

these mechanisms are entirely natural and

entirely normal. Periods of low food availability have always been a natural

part of human his...

Otherwise, we would not have survived as a...

except in the case of malnourishment (you should not fast if you’re malnourished, of course, and extreme fasting can cause ma...

it’s merely changing fuel sources, from food to our...

the most effective method of reducing insulin is to avoid all foods altogether.

Lowering insulin also rids the body of excess salt and water because insulin is well known to cause salt and water retention in the kidneys.