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

by Jason Fung

Hunger is not so simple as “the longer you don’t eat, the hungrier you’ll be.” Hormonal regulation of hunger plays a key role.

So the optimal strategy seems to be eating the largest meal in the midday, sometime between noon and 3:00 p.m., and only a small amount in the evening hours. Interestingly, this is the traditional Mediterranean eating pattern. They eat a large lunch, followed by a siesta in the afternoon, and then have a small, almost snack-sized dinner. While we often think of the

Mediterranean diet as healthy due to the type of foods in it, the timing of meals in the Mediterranean may also play a role.

You start the morning with a large cup of coffee, skipping breakfast, then work right through lunch and get home in time for dinner. This saves both time and money. There is no cleanup or cooking for breakfast. You’ll be home for dinner

without anybody even realizing you were fasting.

You could follow this regimen daily, although most will get good results doing a twenty-four-hour fast two to three times per week. Brad Pilon, the author of Eat, Stop, Eat, recommends using a twenty-four-hour fast twice a week.

5:2 diet consists of five normal eating days. On the other two “fast” days, women may eat up to 500 calories per day and men up to 600 calories.

Ketones have sometimes been referred to as a “superfuel” for the brain. Ketones generally require thirty-six to forty-eight hours of fasting to ramp up.

Incorporating intermittent fasting (16:8 and 20:4) and heavy lifting / interval training (to preserve muscle mass and drain those glucose stores)

From a practical standpoint, it seems rather harsh to end a fast as soon as you have passed its most difficult day. Instead, we encourage patients to continue their fast for seven to fourteen days. A fourteen-day fast delivers seven times the benefit of a two-day fast but is only marginally more difficult.

Headaches are common the first few times you fast. It is believed that they’re caused by the transition from a relatively high-salt diet to very low salt intake on fasting days.

Can I exercise while fasting?

Following a very low carbohydrate diet, or ketogenic diet, trains your body tissues to burn fat.

You can store far more energy in the form of fat than in glycogen, and for endurance athletes, the increase in available energy when they start burning fat is a significant advantage.

What has happened in the past fifty years or so is that we have kept all the feasting but eliminated all the fasting. The normal balance has been perturbed, and obesity is the predictable outcome. If you feast, you must fast. That’s really all there is to it.

But we must balance the periods of eating a lot with periods of eating very little. It’s all a matter of balance.