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

by Jason Fung

Advantage #1: It’s Simple

Eat nothing. Drink water, tea, coffee, or bone broth.

Advantage #4: You Can Enjoy Life’s Little Pleasures

fasting restores the ability to occasionally enjoy that dessert by balancing out the feast.

is, after all, the cycle of life. Feasts follow fasts. Fasts follow feasts.

This is how we have always lived. Birthdays, weddings, holidays, and other special occasions have always, throughout human history, been celebrated with feasts. ...

You can indulge yourself, as long you balance that with some abstinence.

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

there’s no maximum amount of time that you can fast. The world record for fasting was 382 days, during which the patient suffered no ill effects.

something, it simplifies our life. It adds simplicity where other diets add complexity.

Fasting, on the other hand, is completely within your control; you may fast or stop fasting anytime you wish.

So we have two incontrovertible facts: Fact #1—Over the past twenty years, conventional weight-loss advice has called for eating less and moving more. Fact #2—Over the past twenty years, obesity rates have exploded.

Six years after their almost miraculous weight loss, thirteen of the fourteen contestants studied had regained the weight they’d lost. This is a failure rate of 93 percent.

two distinct ways energy is stored in the body: as glycogen in the liver and as body fat.

Both body fat and glycogen are used for energy in the absence of food, but they aren’t used equally or at the same time.

You need to (mostly) empty out the fridge before you can use what’s in the freezer—you need to burn most of the glycogen before you can burn fat. In essence, the body can burn either sugar or fat, but not both.

After a week or two of fasting for 19 hours a day and eating only within a 5-hour window, I was surprised to see that my excess weight had clearly started to melt away.

If insulin levels are abnormally low, then fat is continually burned.

high insulin levels prevent the body from accessing the fat

High Insulin + Reduced Calories = Slowing Metabolism

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.

When either food or glycogen is available, we do not use our less-accessible fat stores.

as insulin resistance progresses, the resulting high insulin levels make it harder and harder to access the fat stores.

This is why insulin resistance plays such a crucial role in obesity: the high insulin levels tell your body to hang onto body fat and simultaneously trigger the body to lower your metabolism. This inexorably erodes weight-loss efforts. Body weight plateaus and then ruthlessly climbs back up, even as the proper diet is maintained.

The main issue is how to get access to the energy locked away in the fat. Insulin is the crucial factor to consider here, not the number of calories you eat.

This explains why the Biggest Loser contestants, just like all dieters using the “eat less, move more” approach, gained their weight back: their metabolism slowed down in response to caloric reduction.

As you increase your calories slightly, you are still eating less than you used to, but because of the slowed metabolism, now you are gaining weight.

the caloric-reduction strategy has a known 99 percent failure rate,

When we eat, insulin rises and blocks fat-burning, and the body instead burns glucose, which is now freely available from the ingested food.

Both low-carb diets and fasting are able to reduce insulin.

The very low carb diet does remarkably well, providing you 71 percent of the benefits of fasting, without actual fasting.

Insulin is the main driver of obesity and diabetes.

Fasting is simply the most efficient and effective way to lower insulin levels.

fasting is often effective when simple caloric reduction is not. Why?

The short answer is that when you’re eating regularly, even if you’re eating fewer calories, you’re not getting the beneficial hormonal changes of fasting.

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

Blood sugar and insulin levels go down as the body changes from burning sugar to burning fat. All this begins to address the long...

The study compared the effectiveness of daily caloric reduction and intermittent fasting among 107 women. One group reduced their daily caloric intake from 2,000 calories to 1,500 calories. The other group was allowed normal caloric intake (2,000 calories) five days a week but only 25 percent of that (500 calories) on the remaining two days—this is referred to as a 5:2 fast.

This means that over the course of a week, average caloric intake for the two groups was very similar: 10,500 calories per week for the reduced-calorie group and 11,000 calories per week for the fasting group. Both groups consumed similar Mediterranean-style diets with 30 percent fat.

After six months, both groups had similar levels of weight loss and fat loss. But the 5:2 fasting group showed a clear, substantial improvement in insulin levels and insulin resista...

Over time, fasting reduces insulin levels more effectively than calorie restriction.

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.

combining a high-fat, low-carb nutrition plan with intermittent fasting and strategic strength training can result in

rapid and dramatic fat loss. Bariatric Surgery: An Argument for

Fat loss during fasting averages approximately ½ pound per day. If you are losing 1 pound or more a day, the excess above ½ pound is water weight and will rapidly be regained upon eating. This is not abnormal or unusual. Don’t be disappointed when the water weight returns or decide that fasting doesn’t work.

fasting can benefit your brain and help your body stay younger.

when I began fasting through the morning, I immediately noticed a significant increase in mental focus, energy, and productivity.

I’m impressed by the mental benefits of fat-adaptation and intermittent fasting.

Humans, like all mammals, have an increase in mental activity when hungry and a...