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Fasting is voluntarily not eating food for varying lengths of time. Fasting is used as a medical therapy for many conditions. It is also a spiritual practice in many religions.


Fasting can be used for nearly every chronic condition, including allergies, anxiety, arthritis, asthma, depression, diabetes, headaches, heart disease, high cholesterol, low blood sugar, digestive disorders, mental illness, and obesity. Fasting is an effective and safe weight loss method. It is frequently prescribed as a detoxification treatment for those with conditions that may be influenced by environmental factors, such as cancer and multiple chemical sensitivity. Fasting has been used successfully to help treat people who have been exposed to high levels of toxic materials due to accident or occupation. Fasting is thought to be beneficial as a preventative measure to increase overall health, vitality, and resistance to disease. Fasting is also used as a method of mental and spiritual rejuvenation.



Used for thousands of years, fasting is one of the oldest therapies in medicine. Many of the great doctors of ancient times and many of the oldest healing systems have recommended it as an integral method of healing and prevention. Hippocrates, the father of Western medicine, believed fasting enabled the body to heal itself. Paracelsus, another great healer in the Western tradition, wrote 500 years ago that "fasting is the greatest remedy, the physician within." Ayurvedic medicine, the world's oldest healing system, has long advocated fasting as a major treatment.
Fasting has also been used in nearly every religion in the world, including Christianity, Judaism, Buddhism, and Islam. Many of history's great spiritual leaders fasted for mental and spiritual clarity, including Jesus, Buddha, and Mohammed. In one of the famous political acts of the last century, the Indian leader Mahatma Gandhi fasted for 21 days to promote peace.
Fasting has been used in Europe as a medical treatment for years. Many spas and treatment centers, particularly those in Germany, Sweden, and Russia, use medically supervised fasting. Fasting has gained popularity in American alternative medicine over the past several decades, and many doctors feel it is beneficial. Fasting is a central therapy in detoxification, a healing method founded on the principle that the build up of toxic substances in the body is responsible for many illnesses and conditions.
The principle of fasting is simple. When the intake of food is temporarily stopped, many systems of the body are given a break from the hard work of digestion. The extra energy gives the body the chance to heal and restore itself, and burning stored calories gets rid of toxic substances stored in the body.
The digestive tract is the part of the body most exposed to environmental threats, including bacteria, viruses, parasites, and toxins. It requires the most immune system support. When food is broken down in the intestines, it travels through the blood to the liver, the largest organ of the body's natural detoxification system. The liver breaks down and removes the toxic by-products produced by digestion, including natural ones and the chemicals now present in the food supply. During fasting, the liver and immune system are essentially freed to detoxify and heal other parts of the body.
Many healers claim that fasting is a particularly useful therapy for Americans and for the modern lifestyle, subjected to heavy diets, overeating, and constant exposure to food additives and chemicals. Some alternative practitioners have gone so far as to estimate that the average American is carrying 5-10 pounds of toxic substances in their bodies, for which fasting is the quickest and most effective means of removal.

Physiology of fasting

Through evolution, the body became very efficient at storing energy and handling situations when no food was available. For many centuries, fasting was probably a normal occurrence for most people, and the body adapted to it. It is estimated that even very thin people can survive for 40 days or more without food. The body has a special mechanism that is initiated when no food is eaten. Fasting is not starvation, but rather the body's burning of stored energy. Starvation occurs when the body no longer has any stored energy and begins using essential tissues such as organs for an energy source. Therapeutic fasts are stopped long before this happens.
Many physiological changes occur in the body during fasting. During the first day or so, the body uses its glycogen reserves, the sugars that are the basic energy supply. After these are depleted, the body begins using fat. However, the brain, which has high fuel requirements, still needs glucose (sugars converted from glycogen). To obtain glucose for the brain, the body begins to break down muscle tissue during the second day of the fast. Thus, during fasting some muscle loss will occur. To fuel the brain, the body would need to burn over a pound of muscle a day, but the body has developed another way to create energy that saves important muscle mass. This protein-sparing process is called ketosis, which occurs during the third day of a fast for men and the second day for women. In this highly efficient state, the liver begins converting stored fat and other nonessential tissues into ketones, which can be used by the brain, muscles, and heart as energy. It is at this point in the fast that sensations of hunger generally go away, and many people experience normal or even increased energy levels. Hormone levels and certain functions become more stable in this state as well. The goal of most fasts is to allow the body to reach the ketosis state in order to burn excess fat and unneeded or damaged tissue. Thus, fasts longer than three days are generally recommended as therapy.
Weight loss occurs most rapidly during the first few days of a fast, up to 2 pounds per day. In following days, the figure drops to around 0.5 pound per day. An average weight loss of a pound a day for an entire fast can be expected.

Performing a fast

Fasts can be performed for varying lengths of time, depending on the person and his or her health requirements. For chronic conditions, therapists recommend from two to four weeks to get the most benefits. Seven-day fasts are also commonly performed. A popular fasting program for prevention and general health is a three-day fast taken four times per year, at the change of each season. These can be easily performed over long weekends. Preventative fasts of one day per week are used by many people as well.
Juice fasts are also used by many people, although these are not technically fasts. Juice fasts are less intensive than water fasts because the body doesn't reach the ketosis stage. The advantage of juice fasts is that fruit and vegetable drinks can supply extra energy and nutrients. People can fit a few days of juice fasting into their normal schedules without significant drops in energy. Juice fasts are also said to have cleansing and detoxifying effects. The disadvantage of juice fasts is that the body never gets to the ketosis stage, so these fasters are thought to lack the deep detoxification and healing effects of the water fast.
Medical supervision is recommended for any fast over three days. Most alternative medicine practitioners, such as homeopaths, naturopathic doctors, and ayurvedic doctors, can supervise and monitor patients during fasts. Those performing extended fasts and those with health conditions may require blood, urine, and other tests during fasting. There are many alternative health clinics that perform medically supervised fasts as well. Some conventional medical doctors may also supervise patients during fasts. Costs and insurance coverage vary, depending on the doctor, clinic, and requirements of the patient.


Fasts must be entered and exited with care. To enter a fast, the diet should be gradually lightened over a few days. First, heavy foods such as meats and dairy products should be eliminated for a day or two. Grains, nuts, and beans should then be reduced for several days. The day before a fast, only easily digested foods like fruits, light salads, and soups should be eaten. During the fast, only pure water and occasional herbal teas should be drunk.
Fasts should be ended as gradually as they are entered, going from lighter to heavier foods progressively. The diet after a fast should emphasize fresh, wholesome foods. Fasters should particularly take care not to overeat when they complete a fast.


Fasting isn't appropriate for everyone and, in some cases, could be harmful. Any person undertaking a first fast longer than three days should seek medical supervision. Those with health conditions should always have medical support during fasting. Plenty of water should be taken by fasters since dehydration can occur. Saunas and sweating therapies are sometimes recommended to assist detoxification, but should be used sparingly. Those fasting should significantly slow down their lifestyles. Taking time off of work is helpful, or at least reducing the work load. Fasters should also get plenty of rest. Exercise should be kept light, such as walking and gentle stretching.

Side effects

Those fasting may experience side effects of fatigue, malaise, aches and pains, emotional duress, acne, headaches, allergies, swelling, vomiting, bad breath, and symptoms of colds and flu. These reactions are sometimes called healing crises, which are caused by temporarily increased levels of toxins in the body due to elimination and cleansing. Lower energy levels should be expected during a fast.

Research and general acceptance

The physiology of fasting has been widely studied and documented by medical science. Beneficial effects such as lowered cholesterol and improved general functioning have been shown. Fasting as a treatment for illness and disease has been studied less, although some studies around the world have shown beneficial results. A 1984 study showed that workers in Taiwan who had severe chemical poisoning had dramatic improvement after a ten-day fast. In Russia and Japan, studies have demonstrated fasting to be an effective treatment for mental illness. Fasting has been featured on the cover of medical journals, although mainstream medicine has generally ignored fasting and detoxification treatments as valid medical procedures.
The majority of research that exists on fasting is testimonial, consisting of individual personal accounts of healing without statistics or controlled scientific experiments. In the alternative medical community, fasting is an essential and widely accepted treatment for many illnesses and chronic conditions.



Fasting Center International. 32 West Anapurna St., #360, Santa Barbara, CA 93101.

Key terms

Ayurvedic medicine — A traditional healing system developed in India.
Toxin — A substance that has poisonous effects on the body.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
Alternative medicine A period of voluntary abstinence from foods and/or drinks; fasting is integral to many religions, as it is believed to purify the mind and spirit; fasting rests the GI tract, and may rid the body of toxins and undigested metabolites; fasting leads to a loss of water, Na+, and K+, resulting in postural hypotension, and decreased blood sugar resulting in depression, fatigue, decreased libido, and malaise, increased nitrogen in the circulation due to protein breakdown, and may result in premature childbirth—Yom Kippur effect
Contraindications Children, pregnancy, lactating women, in elderly, and in those with asthma, cancer, diabetes, eating disorders, schizophrenia, tuberculosis, ulcerative colitis
Lab medicine A period during which no food or beverages—often including water—is ingested for a period of 8 to 14 hours
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


V. refraining from taking food. So long as water is taken, reasonably well-nourished people can safely fast for several days. Once the fat stores are depleted, however, the voluntary muscles are consumed and soon become severely wasted. Many people find moderate regular fasting a useful aid to health.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Patient discussion about fasting

Q. Is it true that fasting (occasionally) is good for health? Many people say that fasting helps the body clean itself, it there a truth behind this?

A. Fasting does help "clean" the intestine for a short period of time. I cannot say it is especially recommended medically-wise to fast every now and then, because our bodies are functioned to digest food and there is usually no problem doing so, and an occasional fast does not show any benefitial healthy effects on the GI system.

Q. how to loose a beer gutt fast!

A. exercise by doing high intensity interval training and cut back on eating junk and drinking beer.

Q. What is a fast and effective way to get bigger biceps and triceps? I am one of the regular goers to gym for the past 6 months and I am very fond of disposing my biceps and triceps. What is a fast and effective way to get bigger biceps and triceps?

A. I would not do any curls at all. Instead focus on multi joint, compound movements. Try back workouts, pull ups, chin ups, etc.

These will work your biceps. Make sure to go as heavy as possible without hurting yourself, and consume protein. The rest and drink alot of water. Sleep adequately.

More discussions about fasting
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References in periodicals archive ?
This study reviewed the understanding of preoperative fasting instructions in 100 day-procedure patients, all of whom had been requested to fast for general anaesthesia.
(2.) Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures: An Updated Report by the American Society of Anesthesiologists Task Force on Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration.
To evaluate the preoperative fasting practices employed in our hospital.
Our case report presents cases that may reinforce a more liberal approach to preoperative fasting as it reflects a potential exaggeration in fasting time for solids but is indeed not enough to support any changes to the current recommendations.
The researchers collected the anaesthesia and nursing forms on a weekly basis and recorded the relevant information, which included patient demographics, operation starting time, time preoperative fasting of solid foods and clear fluids was prescribed to commence, and time the patient last ingested food or clear fluids preoperatively.
Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: a report by the American Society of Anesthesiologist Task Force on Preoperative Fasting.
We have previously conducted an audit of 200 elective general surgery patients in a busy district general hospital (DGH) on the length of preoperative fasting and confirmed that patients were fasting for much longer than necessary (Khoyratty et al 2010).
Modern preoperative fasting guidelines: a summary of the present recommendations and remaining questions.
ERAS compliance definitions (adapted from 3) ERAS Included Individual Definitions of ERAS Compliance for Items Included Individual Items 1 Presurgical education Received verbal and written ERAS education at a dedicated preadmission visit 2 Presurgical optimisation Patients stopped smoking 4 weeks before surgery, and alcoholics ceased all alcohol consumption 4 weeks before surgery 3 Preoperative fasting Preoperative fasting limited to 2 hours for clear liquids (water, coffee, juice without pulp), and at 6 hours for solids 4 Patient blood management Set of measures applied to optimise preoperative haemoglobin, avoid bleeding and avoid transfusion 5 Preoperative carbohydrate Given preoperative carbohydrate drinks preload drink.
Among the major components of ERAS practices and protocols are limiting preoperative fasting, employing multimodal analgesia, encouraging early ambulation and early postsurgical feeding, and creating culture shift that includes greater emphasis on patient expectations.
It has been suggested that minimising the preoperative fasting period, by allowing the consumption of oral carbohydrate-containing clear fluids with or without protein, has a number of clinical advantages, including more stable haemodynamics during induction of anaesthesia, greater glycaemic stability, reduced lean tissue catabolism, and a more positive patient experience.