Fasting

Fasting is the oldest of the practices and the simplest. You stop eating for a while. That is all. Almost everyone who does it seriously discovers the same thing: the body and the mind are not two things, and an empty stomach opens a door that nothing else opens.

Jesus fasted forty days in the wilderness before he said a public word. He assumed his followers would fast (when you fast, not if), and his only instruction was to keep it secret and look cheerful while doing it. The early church fasted twice a week. Nearly every tradition on earth fasts. The question is how.

Why an empty stomach helps

Three things happen when you stop eating, and they build on each other.

The body gets quiet. Digestion is work, the biggest single thing your body does after a meal. Stop feeding it, and after a few hours that energy is freed. Many people notice a particular clarity at the 14- to 20-hour mark: the mind feels lighter, sharper, less padded.

The appetite gets exposed. You discover how much of your eating was not hunger at all but habit, boredom, anxiety, and the wish to not feel something. The fast makes the wish visible, and once it is visible you can do something with it besides eat.

A second hunger appears. Somewhere past the first day, food-hunger quiets and another comes forward: for meaning, for presence, for God. You had been feeding it with meals. Now it speaks in its own voice. Man shall not live by bread alone. This is the discovery every serious faster makes and the reason fasting and prayer have always gone together.

What the body is doing

It helps to know that the body is not in trouble. It is doing something it was built to do, and the science of it is well mapped.

You carry weeks of fuel. An ordinary adult stores well over a hundred thousand calories as fat, enough for more than forty days, along with a day’s worth of quick fuel in the liver. Nobody is running on empty by lunchtime. What feels like emptiness is a signal, not a shortage.

The fuel changes over. For the first day the liver’s stored sugar keeps the blood steady. As it runs down, the body begins making its own glucose from other materials, and the fat stores open. The liver turns fat into ketones, and by the second and third day ketones are supplying a growing share of the body’s energy, including the brain’s. The old idea that the brain can only run on sugar is simply wrong; after a few days of fasting a quarter of its fuel is ketones, and after weeks, most of it. Blood sugar drifts lower and stays there, and in a healthy adult this almost never causes symptoms, because the brain has switched fuel. The one exception is anyone taking medicine that lowers blood sugar, which is why the caution below is not optional.

The hormones move the right way. Insulin, the hormone that stores fat and keeps it locked away, falls within a day. Growth hormone, which protects muscle, rises several-fold over a two-day fast. Adrenaline rises a little and, for the first two or three days, the body actually burns slightly more energy at rest, not less. This is the alertness people report: the mind sharpens because the body is preparing you to go and find food, not to lie down.

Hunger follows the clock, not the fast. The hunger hormone rises at your usual mealtimes and then falls on its own whether or not you eat. Across a day of fasting the waves get lower, not higher. In a study of more than fourteen hundred people who fasted for between four and twenty-one days on water, broth and a little juice, ninety-three percent said they were not hungry; the hunger and headaches came in the first days and then left, and their sense of well-being rose. The second day is the hard one. By the third and fourth most people feel unexpectedly good.

Done properly, it is safe. Across roughly two thousand medically supervised fasts of two to forty days, there were no deaths and a handful of hospital admissions. Fasting has real hazards, and they are listed plainly below, but they are known and avoidable: the wrong medicine on the wrong day, too little salt, too much too fast at the end. The body itself knows what to do.

The ladder

Do not begin with forty days. Begin at the bottom and climb slowly. Each rung is a complete practice in itself; most people live at the first two for life and occasionally visit the third and fourth.

The daily fast

Stop eating after supper and do not eat again until midday or a little before: a window of roughly sixteen hours, most of which you sleep through. It is how most humans ate for most of history, and it is the single most useful thing you can do to prepare for stillness, because it means every morning you wake fasting, with a quiet body and a clear mind, and the hour before dawn is yours.

If sixteen hours is hard, begin at twelve and lengthen by an hour a week. Black coffee and plain tea are fine. Anything with calories ends the fast. Eating your meals earlier rather than later does more good than the same meals eaten late; the body handles food best in the morning and worst at night.

One honest word about what this does and does not do. A daily eating window helps people eat less without trying, steadies blood sugar, and lowers blood pressure a little. The studies find these effects real and modest. Its great gift is not to the waistline but to the morning.

Sunset to sunset

The weekly fast of the early church. The Didache, one of the oldest Christian documents outside the New Testament, tells believers to fast on Wednesdays and Fridays. Finish supper on the eve, eat nothing the next day, and break the fast gently at supper. It is twenty-four hours, and you will find that the hunger comes in waves at your usual mealtimes and passes if you let it.

Give the missed meals away. Isaiah 58 makes this a condition of the whole business: the fast God chooses ends in shared bread. The money or the time you did not spend on eating should go to someone who needs it.

A day and a half

When the day fast has become easy, there will be an evening when supper comes round and you are simply not hungry. Skip it, sleep, and eat the next morning. That is thirty-six hours, and it is the rung where the body goes fully over to its stores: ketones are climbing, growth hormone is up, and the second hunger is close. It costs little more than the day fast and gives much more. Once a week is a serious practice; once a month is a good one. Take salt in your water on the second morning if you feel lightheaded.

The Daniel fast

In the book of Daniel, the young exiles refuse the king’s rich food and ask for vegetables and water for ten days, and at the end they are healthier than the men who feasted. The Daniel fast is a fast from richness rather than from food: plants, whole grains, legumes, nuts, oil, water. No meat, no dairy, no sugar, no wine, nothing refined. It is the right fast for anyone who cannot safely stop eating, and a good way to spend Lent. The eating chapter describes the table.

Three days

Seventy-two hours on water is where fasting becomes serious. Past that point the body has fully shifted to burning its stores, the hunger has mostly gone quiet, and the second hunger is loud. It is also the edge of what should be done without a clinician involved, and if you take any daily medicine at all, it is past that edge: get a plan from whoever prescribes it before you begin.

Salt is the thing people get wrong. As insulin falls the kidneys let go of sodium and water, which is why you urinate more and why the headache, the cramps and the dizziness on standing arrive. From the second day, take half to one teaspoon of salt through the day, dissolved in water or as a cup of salted vegetable broth. Plain water without salt is not the answer; drink to thirst, two litres or so, and no more. A little magnesium is fine if you like it. Leave potassium to a clinician who is measuring it.

Rest more than you think you need. Walk, stretch, do light chores; do not run, lift heavy or sit in a sauna. Stand up slowly. If you take blood-pressure medicine, check your pressure morning and evening; it will fall, and your prescriber may want to lower the dose. Break the fast over a full day: broth, then cooked vegetables and fruit, then a small meal.

The forty

Jesus’s forty days were water-only, in the desert, alone. Moses and Elijah fasted the same span. It is the wilderness number, a span long enough that whatever you carried in with you has to be set down.

Very few people should attempt this as a water fast, and no one should attempt it without medical supervision. Anything beyond about a week on water needs a clinician, daily attention to salt and potassium, and a thiamine tablet each day, because the body’s store of that one vitamin runs out in a few weeks and its loss injures the brain. The refeeding at the end is itself a medical matter after a long fast. What most people mean today by a forty-day fast is a modified one: the Daniel fast for forty days, or a daily fast for forty days, or twenty-four-hour fasts on a schedule. The forty-day journey on this site is built that way. It climbs the ladder gradually and never asks for more than a day and a half without food. That is the point: forty days of practice you can keep will change you more than three days of heroics followed by a month of recovery.

How to do it well

Eat clean for a fortnight first. The first real fast is far easier if you have already dropped sugar, refined flour and packaged food for a week or two. The headache, fatigue and irritability that people blame on fasting are mostly the withdrawal from those, and it is better to go through it while still eating. The eating chapter describes the table.

Prepare the day before. Eat simply, eat a little less, and finish supper early. A heavy last meal makes the first day of any fast worse.

Decide before you begin. Set the length, say it aloud, and tell no one. A fast with a decided end is a practice; a fast with a vague end is a negotiation you will lose at four in the afternoon.

Know your cues. Most of what feels like hunger at three in the afternoon is a habit: the sofa, the car, the kitchen at nine, the friend who says “just one.” Decide in advance what you will do at each. Habits are contagious; people whose close friends fast find it far easier than people whose close friends do not.

Drink water, and after the first day, salt. A great deal of what feels like hunger during a fast is thirst, and most of what feels like weakness is missing salt. Water to thirst; a pinch of salt in it on any fast past a day, half a teaspoon or more a day on anything past two.

Coffee and tea are fine, black. A spoon of coconut or MCT oil in the morning coffee blunts hunger and does not raise insulin, though strictly it is food; call it a softened fast and do not pretend otherwise.

Move gently. Walk, stretch, garden. Save hard training for eating days.

Keep the hour. Use the time you would have spent eating for the thing the fast is for: sit, read a paragraph of the gospels slowly, walk without your phone. If you fast and simply work harder to distract yourself, you have dieted, not fasted.

Anoint your head. His only instruction. Dress well, be kind, be more cheerful than usual. The fast is a secret between you and the one who sees in secret.

Break it gently. Broth or fruit first. Then something small. For every three days fasted, give a day to light eating before ordinary meals return. The first meal after a fast is one of the great pleasures available to a human being; do not spoil it by overeating.

Stop, and get help, if you faint or the dizziness does not clear when you lie down; if your heart races or your chest hurts; if you cannot keep water down; if you become confused, see double or cannot walk straight; if a joint swells hot; if you have severe belly pain. None of these is the fast working. All of them are the body asking you to end it.

What to do with the hunger

This is the spiritual technique, and it is the same technique used in the stillness chapter for thoughts.

When hunger comes, and it comes in waves, usually at the hours you normally eat, do not fight it and do not feed it. Turn toward it. Notice where it is in the body. Notice that it is a sensation, not an emergency. Say a word to it if you like: not by bread alone. And then let it be there while you go on with what you were doing. Within twenty minutes it will have passed. Every time you do this, you learn something that cannot be learned any other way: that a want can be felt fully and not obeyed. That is the beginning of freedom, and it transfers to every other want you have.