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

by Jason Fung

By “small amount,” we mean 1 to 2 teaspoons of cream or coconut oil—nowhere near the copious amounts of f...

see here for a recipe.

but do not add bouillon cubes, which are full of artificial flavors and monosodium glutamate. Beware of canned broths: they are poor imitations of the homemade kind.

Sea salt also contains other trace minerals, such as potassium and magnesium, which may be particularly beneficial during fasting. (For shorter fasts, such as the twenty-four- and thirty-six-hour variety, it probably makes little difference.)

so technically, any fast that allows broth is not a true fast. But many people have found that the broth makes a longer-duration fast much more bearable.

What matters most is our insulin response to food, since obesity is largely a problem of excessive insulin.

Prolonged fasting may range from one week to one month.

I categorize fasting periods as short (less than twenty-four hours) or long (more than twenty-four hours), but this is somewhat arbitrary.

shorter regimens are generally used by those mostly intere...

Your hunger signals will become more regular—that is, they’ll adjust to the fasting and you’ll start to become hungry when your body is ready to eat, rather than from “false” signals being driven by wild fluctuations in insulin, blood glucose, and stress hormones.

People were eating three meals and three snacks daily, and insulin levels were beginning to be kept perpetually high. Over time, the constant stimulation of insulin leads to the development of insulin resistance, which leads back to high insulin levels, which, in turn, leads to obesity.

the combination of whole foods, lower-carbohydrate diets, less added sugars, and a daily twelve-hour fast was enough to prevent most Americans in the 1950s and 1960s from developing obesity—even though they still ate plenty of white bread and jam, and whole-wheat bread was rare and whole-wheat pasta unheard-of.

Eating the largest meal in the evening seems to cause a much larger rise in insulin than eating earlier.

personal experience and studies show that hunger is lowest in the morning,

Hunger follows a natural, circadian rhythm that is independent of the eat/fast cycle.

Ghrelin, the hunger hormone, rises and falls in a natural circadian rhythm, with a low at 8:00 ...

hunger typically falls to its lowest level at 7:50 a.m. and...

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.

Nutrient deficiency is not a major concern with a twenty-four-hour fast. Since you are still eating daily, you just need to make sure that during that meal you consume adequate proteins, vitamins, and minerals by eating nutrient-dense, natural, unprocessed foods.

You could follow this regimen daily, although most will get good results doing a twenty-four-hour fast two to three times per week.

The reason a limited number of calories are allowed on fast days is to increase compliance.

I’ve found that people are more capable of fasting than they may think, the 5:2 diet can be a good way to ease into fasting.

She guided men and women through an alternate-day fasting protocol for one month. After that, they continued with the protocol on their own for the next thirty days. At the end of those thirty days (two months total on the protocol), weight loss averaged 12.6 pounds. Importantly, lean mass (muscle, protein, and bone) remained unchanged—that weight loss was purely due to loss of fat.

So I think it’s important to keep an eye on allostatic load when considering what duration of fast one might tackle.

In our IDM Program, we use thirty-six-hour fasts, on a three-times-a-week schedule, with patients who have type 2 diabetes. We continue this schedule until the desired results are achieved: the patient is able to go off of all diabetes medication and has reached the desired weight.

Extended fasts—those lasting longer than forty-two hours—

so by lowering insulin levels,

fasting helps the body excrete excess salt and water. During the first several days of fasting, there’s a corresponding increase in urine flow.

In the 1970s, a twenty-seven-year-old Scottish man started fasting at a weight of 456 pounds.

next 382 days, he subsisted on only noncaloric fluids, a daily multivitamin, and various supplements, setting the world record for the longest fast.

456 pounds to 180 pounds.

Even five years after his fast, he remained at 196 pounds.

we tell patients to expect an average fat loss of half a pound per day of fasting.

During extended fasting, the brain reduces its reliance on glucose as an energy source.

believed that the brain is able to more efficiently use these ketones, possibly leading to improved mental abilities.

Ketones generally require thirty-six to forty-eight hours of fasting to ramp up.

Extended fasting rarely causes electrolyte abnormalities.

Blood magnesium levels occasionally go low.

often supplement patients with magnesium to be on the safe side.

This also reflects the fact that the body is recycling all the essential fats

and amino acids from the breakdown of old or dysfunctional cells.

Instead, we encourage patients to continue their fast for seven to fourteen days.

much of the organ damage caused by diabetes is irreversible once it occurs.

we advise patients to switch to an alternate-day fasting regimen for two weeks before repeating an extended fast.

Refeeding Syndrome

Americans in Japanese prisoner of war camps

longstanding anorexia nervosa and of alcoholic patients.

they are often malnourished and do not have significant body fat ...

This syndrome is extremely uncommon in patients with adequate body fat stores who are well-nourished.

Refeeding syndrome occurs when electrolytes, particularly phosphorus, are depleted due to malnourishment.