Strictly defined, fasting is abstinence from all food and drink (except water) for a limited period of time to maintain or improve health, or treat a specific illness. Juice fasting, a popular variation, is abstinence from all food and drink except water, vegetable juices, and fruit juices. A modified fast includes small amounts of solid food, usually raw fruits as well as raw and steamed vegetables. Some advocates of fasting include other modifications as well, such as vegetable broth, herbal teas, and nutritional supplements. Most of the research into the therapeutic value of fasting has explored the water-only method.
A short fast, lasting from one to three days, can generally be tolerated by most people. An extended fast (more than three days) should be supervised by a doctor, preferably one trained in fasting therapy.
Fasting has been known since ancient times. In fact, there are references to it in the Bible, the Koran, and ancient Chinese and Greek medical texts. Historically, people have fasted as part of religious rituals, as a way of expressing grief, and as part of political protests. Fasting to benefit health is a relatively new practice and is generally undertaken only in prosperous Western societies.
One of the first doctors in the United States to advocate fasting was Isaac Jennings, M.D. (1788-1874) of Fairfield, Connecticut. Jennings rejected the therapeutic use of drugs to treat specific ailments and instead developed a treatment program that included periodic fasting, a vegetarian diet, pure water, sunshine, clean air, exercise, and rest. His program, which came to be known as the Natural Hygiene system, is still practiced today, and doctors who follow it usually specialize in overseeing therapeutic fasts.
Perhaps the best-known modern proponent and practitioner of therapeutic fasting was Herbert M. Shelton (1895-1985), a chiropractor and naturopath who developed a strict (water only) fasting protocol in the late 1920s. In 1928, Shelton founded his own health school and in 1948 he helped to establish the American Natural Hygiene Society to further promote fasting and a holistic lifestyle to a lay public. In 1978, he formed a professional branch, today known as the International Association of Hygienic Physicians (IAHP). The organization publishes research on fasting and provides certification in fasting therapy to physicians in the fields of medicine, osteopathy, chiropractic, and naturopathy.
How Does Fasting Work?
Critics of fasting therapy often confuse fasting with starvation. In the fasting state, nonessential tissue, like fat, is used for fuel while vital organs are spared. Starvation occurs when the body has depleted its fat stores and begins to use vital organs for fuel. Obviously, if the body does not receive food after a supervised fast, starvation and death will inevitably follow.
The series of physiologic events that occurs within the body during a fasting state has been well-studied and follows a definite sequence. Basically, the body undergoes certain changes in metabolism to conserve its energy sources but continues to function with the same degree of efficiency. For example, blood sugar levels remain fairly constant no matter how long the fast lasts.
Early in fasting, the body both manufactures glucose (gluconeogenesis) and releases stores of it from within the liver (glycogenolysis). After a few days, the body will release triglycerides from fat cells. These tryglycerides become oxidized and form acids called ketones, which are then used for energy production. All of these changes slow the overall metabolism of the body to about 75% of its normal rate. For this reason, plenty of rest (and no vigorous exercise) is routinely advised while fasting.
Health Benefits of Fasting?
Published research into therapeutic fasting first appeared in the late nineteenth century. Since that time articles have appeared in conventional medical journals in both the United States and Europe showing the positive results of supervised fasting in treating various diseases, including obesity, cardiovascular disease, autoimmune disorders, diabetes, skin disease, gastrointestinal disease, arthritis, and allergies. How fasting positively affects these diseases, and what its long-term effects are, depends on the ailment. If you have a chronic medical problem and are interested in the benefits of fasting as a therapeutic modality specific to your condition, your best bet is to locate a nutritionally oriented physician or naturopath with some experience in the field.
There is very little published evidence that fasting has any value for a healthy individual. Even so, practitioners of naturopathic medicine regularly recommend fasting as the therapeutic tool for internal cleansing, otherwise known as detoxification. Periodic fasting, naturopaths believe, helps overworked systems (the gastrointestinal tract, skin, liver, and kidneys) remove potentially damaging toxins from the body.
Not surprisingly, a naturopath's definition of what constitutes a "toxin" vastly exceeds that of conventional medicine. And while both camps tend to agree that certain heavy metals (lead, cadmium, mercury) and chemical compounds (pesticides, herbicides, solvents) are toxic, naturopaths expand the list to include food additives, many commonly prescribed drugs, cigarettes, recreational drugs and alcohol, and substances produced by bacteria-induced chemical reactions in the intestine.
In addition to using fasting for cleansing purposes, many healthy individuals find it a useful way of weaning themselves off of unhealthy foods. A fast of no more than three days can be used to launch a healthier diet–for example, changing to a vegetarian diet from a meat-based regimen.
A fast can also be an effective way to begin a low-calorie diet, a signal to your body that you're altering the way you eat. But the hunger produced from a fast can lead some people to binge afterward. The "yo-yo" effect of fasting and binging can slow down metabolism, making it harder to lose weight in the long run.
What Can I Expect From Fasting?
If you'd like to try a fast of one to three days' duration, it is probably safe to do so on your own–as long as you are healthy and not pregnant or breast-feeding. If you plan to fast for longer than three days, however, you should seek medical supervision.
If your primary-care practitioner isn't willing to supervise your fast, you may want to seek a naturopathic physician, nutritionally oriented chiropractor, nutritionist, or registered dietitian. Before you begin, the practitioner should go over your medical history, conduct a physical examination, and perform other tests to be sure that your body is up to the challenge of a fast.
Prepare for your fast with a day of eating light vegetarian meals, focusing on raw fruits plus raw and steamed vegetables. Throughout your fast, drink plenty of liquids–water, if you are on a strict fast, and nonacidic juices and herbal teas, if you are on a modified fast. While you'll need to continue any prescription medicines for a specific condition, you can stop taking any nutritional supplements during the fast. The way you break your fast is also important. Ease back into solid food the same way you eased into the fast–with light meals of fruits and vegetables. A large amount of food right away may be too much for your system to comfortably handle.
At the beginning of your fast, you may feel energized. Or, your hunger may trigger headaches, dizziness, fatigue, and irritability. As time goes on, you will probably feel calmer and may even experience a heightened sense of well-being and clarity of mind. Your sleep patterns may be disrupted, however. Be sure to nap during the day if your sleep at night is lighter. In addition, your tongue may feel furry or coated, and you may develop bad breath. Rinse your mouth with plain water or water mixed with lemon juice to relieve these symptoms. If dizziness, nausea, aching limbs, or visual or hearing disturbances bother you, contact your practitioner.
Don't expect to pursue your regular activities during a fast. For a weekend fast, you will want to stay close to home. Limit exercise to walks, stretching exercises, yoga, or tai chi. Good pastimes are meditating, napping, reading, and listening to relaxing music.
Cautions about Fasting
- Even healthy individuals should not undertake an extended fast of more than three days without medical supervision.
- Pregnant or breast-feeding women should not fast.
- If you have advanced cancer, a compromised immune system, diabetes, ulcers, or liver, kidney, heart, or lung disease, you should never fast without medical supervision.
- Fasting as part of the treatment for a chronic disease such as heart disease, epilepsy, arthritis, or schizophrenia should be under the supervision of a physician experienced in the field.
- Anyone who takes prescription or recreational drugs regularly should not fast without medical supervision. Withdrawal symptoms can develop quickly during fasting.
- It's important to break a fast carefully. Eating too much too soon will overload your digestive system, causing uncomfortable and disruptive reactions. Your doctor can help you decide how best to break your fast for your individual needs.
Choosing a Fasting Practitioner
Because fasting is not included in conventional medical training, the number of physicians utilizing this therapeutic tool remains very small. While your primary-care physician may be willing to supervise a short fast, if you plan to fast for more than three days, you should consult a naturopathic physician, nutritionally oriented chiropractor, nutritionist, or registered dietitian. Ask your primary-care practitioner for a referral.
A directory of practitioners who specialize in fasting therapy is available through the International Association of Hygienic Physicians (IAHP), in Youngstown, Ohio.