Fasting is defined as abstinence from all food and drink except water for a specific period of time, usually for a therapeutic or religious purpose. This process spares essential tissue (e.g. vital organs) while utilizing non-essential tissue (e.g. adipose tissue, digestive enzymes, muscle contractile fibers, and glycolytic enzymes) for fuel.
Some medical references use the terms fasting and starvation interchangeably. Unlike fasting, starvation is a process in which the body uses essential tissue for fuel. During starvation, the body relies on protein as a major fuel source, as most fat stores have been depleted. If an organism does not receive food at the end of the maximum fasting period (several weeks to months depending on fat stores, metabolism, stress, and activity), starvation follows and death will ensue.
Although the term fasting is used loosely in medical literature, the strictest definition (water only) is the focus of this chapter. Some medical studies recommend supplementation with vitamins, fruit and vegetable juices, acaloric fluids (coffee, tea, etc.), and drugs while the patient is “fasting”. These practices have not been shown to produce any advantage, and serious problems have sometimes occurred, especially when non-essential medication was permitted. (In special cases it may be necessary to maintain the patient on essential medication while fasting, e.g. thyroid, prednisone, and insulin.)
Although therapeutic fasting is probably one of the oldest known therapies, it has been the object of only limited study by the scientific community. The most recent development in the study and promotion of fasting has been the formation of the International Association of Hygenic Physicians (IAHP). This organization comprises doctors specializing in therapeutic fasting as an integral part of total health care. The section on clinical protocol below reflects the format practiced by the IAHP. Any doctor contemplating the use of therapeutic fasting should receive adequate training. The IAHP provides guidelines for doctors interested in this training.
Another recent development has been the work of clinical ecologists who use short-term fasting as part of their diagnosis and treatment of food intolerance.
Throughout history, people of various cultures and religions have recognized the value of fasting. Numerous references occur in the Bible, Koran, pagan writings, and writings of the ancient Greeks.
One of the earliest doctors to use therapeutic fasting in the United States was Isaac Jennings MD (1788–1874). In 1822, Jennings discarded the use of drugs and, through the influence of a Presbyterian preacher, Sylvester Graham (1794–1851), began advocating fasting and other aspects of hygienic treatment (vegetarian diet, pure water, sunshine, clean air, exercise, emotional poise, and rest). This later came to be known as the Natural Hygiene or Hygienic system.
Other doctors who followed in the hygienic tradition included: James C. Jackson (1811–1895), Russell T. Trall (1812–1877), William A. Alcott (1798–1859), Mary Grove Nichols (1810–1884), Thomas L. Nichols (1815–1901), Edward H. Dewey (1837–1904), George H. Taylor (1821–1896), Harriet Austin (1826–1891), Charles E. Page (1840–1925), Emmett Densmore (1837–1911), Helen Densmore (?–1904), Susanna W. Dodds (1830–1915), Felix Oswald (1845–1906), Robert Walter (1841–1921), John H. Tilden (1851–1940), and George S. Weger (1874–1935). Most of these physicians graduated as MDs from eclectic medical schools, and they published various works on hygiene.
Herbert M. Shelton
The hygienic lineage continued into the mid-1900s, mainly due to Herbert M. Shelton (1895–1985), who developed a stricter protocol for fasting (water only; no enemas, exercise, or treatments; and complete rest) and other aspects of hygiene. Shelton began his study of fasting in 1911 by reading the popular writers of his day: Sinclair, Carrington, Hazzard, Haskell, Purinton, Tilden, and MacFadden. He studied under the fasting authorities of his time at MacFadden’s College (Chicago, IL), Crane’s Sanatorium (Elmhurst, IL), and Crandall’s Health School (York, PA). (Among the earliest fasting institutions of this time were MacFadden’s Healthatorium, Tilden’s Health School, Lindlahr’s Nature Cure Sanatoriums, and Lust’s Jungborn – operated by Benedict Lust, the founder of naturopathy in the United States. ) In 1924, he completed doctorates from the American School of Chiropractic and the American School of Naturopathy in New York.
Shelton was a dynamic lecturer, prolific writer, and publisher. He founded (in 1928) a fasting institution and health school which provided services for over 40 years. In 1949, along with William Esser ND DC, Christopher Gian-Cursio ND DC, and Gerald Benesh ND DC, he formed the American Natural Hygiene Society, a lay organization dedicated to preserving the tenets of hygiene. In 1978, a professional branch was formed, the aforementioned International Association of Hygenic Physicians. Today, the IAHP organizes annual meetings, a journal, research and certification for doctors specializing in therapeutic fasting.
Research into fasting has been reported since 1880. Since then, medical journals have carried articles on the use of fasting in the treatment of:
The earliest research was primarily observational; physiologic and metabolic changes were recorded while an individual fasted. These included: Tanner, 40 days (1880); Jacques, 30 days (1887) and 40 days (1888); Penny, 30 days (1905); and Levanzin, 31 days (1912). The earliest record of therapeutic fasting in the medical literature occurred in 1910.
Further investigation into the physiologic changes that accompany fasting was conducted in 1923 at the University of Nebraska by Morgulis. This classic study, Fasting and undernutrition, provides an in-depth analysis of animal and human reactions during fasting.
In 1950, Ancel Keys and colleagues at the University of Minnesota compiled two volumes entitled The biology of human starvation. Thirty-two volunteers fasted for up to 8 months while detailed observations were made. These findings were compared with food deprivation observations which were made during the Second World War. Through their studies, the researchers found that fasting did not cause vitamin or mineral deficiencies and that diabetes and skin diseases improved.
Guelpa recorded the benefits of fasting in diabetes and gout, as well as in inflammation and surgery. The treatment of diabetes with fasting was further explored by Allen in 1915. He noted that rest and fasting usually stopped glycosuria, and he also observed improvements in gangrene and carbuncles.
The treatment of seizures through fasting was begun in the early 1900s in France by Guelpa & Marie (cited by Kernt). In 1924, Hoeffel & Moriarty described fasting’s beneficial effects in epilepsy. In 1928, Lennox, concurring with other researchers, found that the induction of ketosis via fasting decreased the length, severity, and number of seizures.
Fasting for obesity has probably received more attention in the scientific literature than any other aspect. The earliest studies were conducted by Folin & Denis who, in 1915, advocated short fasts as a safe and effective means to lose weight. Bloom, Duncan, Drenick, and Thompson have published numerous works on the use of short and long fasts in obesity. Perhaps the most famous study on obesity appeared in the Postgraduate Medical Journal of 1973, which reported the experience of a 27-year-old male who fasted without complications for 382 days and lost 276 pounds.
In general, weight loss during fasting is initially approximately 0.3% of body weight per day, with a gradual decrease to 0.10%/day after 30 days. The initial weight loss is primarily water and salt. For every pound lost, the body loses approximately 140 g of protein and 250 g of fat.
Although fasting is very effective for weight reduction, fasting alone, without counseling and other lifestyle modifications, does not insure long-term maintenance of the lower weight level. This is well documented in a study of 121 obese patients who were followed for 7.3 years after fasts which had averaged two months. After 2–3 years, 50% had reverted to their pre-fast weight, and by the end of the study 90% had reverted.
Studies of the effects of fasting on patients with heart disease began in the early 1960s. Duncan noted improvements in hypertension and chronic cardiac disease. Others have also found fasting to be beneficial in heart disease, including Gresham, Lawlor, Suzuki, Vessby, and Sorbris. Improvements noted include reduced triglycerides, blood pressure, atheromas, and total cholesterol; increased HDL/cholesterol ratio; and alleviation of congestive heart failure.
In a random trial, in 1984, of 88 patients with acute pancreatitis, fasting was determined to be the treatment of choice. It was suggested that “fasting alone be initially used as the simpler and more economical therapy”. The finding was that “neither nasogastric suction nor cimetidine offer any advantage over fasting alone in the treatment of mild to moderate acute pancreatitis of any etiology.”
PCB and DDT contamination
A most encouraging use of fasting was published in the American Journal of Industrial Medicine in 1984. This study involved patients who had ingested rice oil contaminated with PCBs. All patients reported improvement in symptoms, and some observed “dramatic” relief, after undergoing 7–10 day fasts. This research supports past studies conducted by Inamura of PCB-poisoned patients and indicates the therapeutic effects of fasting. Caution must be used, however, when treating patients known to suffer significant contamination with fat-soluble toxins. DDT is mobilized during a fast and may reach blood levels toxic to the nervous system.
The beneficial effect of fasting in certain autoimmune diseases was reported in Lancet in 1958. The researchers found that fasting shortened the early stages of acute glomerulonephritis (reduced glomerular filtration rate, high blood pressure, and edema), thus improving the prognosis. They concluded that “all patients with acute glomerulonephritis should fast”. Other autoimmune diseases that have responded to fasting include rosacea, lupus, and chronic uticaria.
The subject of arthritis and fasting is receiving greater attention in the scientific literature, with most of the research coming from Scandinavia. Scientists have documented the anti-inflammatory effects of fasting with observations of decreased ESR, arthralgia, pain, stiffness, and need for medication. A 1984 US study of 43 patients with definite or classical rheumatoid arthritis found significant improvement in grip strength, pain, PIP swelling, ESR, and functional activity after a fast of 7 days.
A strong link between arthritis and food intolerance has been revealed through fasting (see also Ch. 51 ). The decrease in symptoms of rheumatoid arthritis during fasting may be due to the decrease in gut permeability which accompanies fasting. This would reduce the absorption of antigenic molecules into the blood from the gastrointestinal tract. In the 1984 Bulletin on Rheumatic Diseases, Panush proposes two theories:
• nutritional modification might alter immune responsiveness and thereby affect manifestations of rheumatic diseases
• rheumatic disease may be a manifestation of a food allergy or hypersensitivity.
Fasting, in conjunction with food challenging, is now being used as a diagnostic test to determine food intolerances. Patients are fasted for a minimum of 4 days, and then individual foods are given to determine if a reaction occurs. This method correlates well with skin prick and RAST testing. A letter in the 1984 Lancet states: 
When food avoidances prevent headaches, IBS, arthralgia and depression, it is more effective and less costly than traditional treatment and the observation also throws light on the etiology of the disorder.
Other diseases in which the scientific literature indicates that fasting has led to improvement include:
• psychosomatic diseases 
• neurogenic bladder
• psoriasis 
• eczema 
• thrombophlebitis 
• varicose ulcers
• neurocirculatory disease
• dysorexia nervosa (impaired or deranged appetite)
• bronchial asthma
• depression 
• neurosis and schizophrenia 
• duodenal ulcers
• uterine fibroids. 
These diseases are not a complete list of indications for fasting, but rather are those that have been studied in the scientific literature. There has been considerable empirical study of fasting in the treatment of a wide variety of diseases. Records of the results can be found in lay, hygienic, and medical literature published since the early 1900s. The vast potential of therapeutic fasting is only beginning to be realized, as recent research reveals such pervasive and important effects as enhancement of immune system function.
The study of the physiology of fasting reveals a highly ordered series of events (see Fig. 47.1 ) which conserve body energy reserves while maintaining the basal metabolic rate (the BMR decreases by about 1%/day during fasting, until it stabilizes at about 75% of normal ). It has been suggested that humans, like other species, have evolved special biochemical pathways to subsist for long periods of time without food. During periods of food scarcity due to climate, injury, illness, etc., animals require adaptive mechanisms to survive. It is now apparent that, in addition to maintaining the BMR, fasting also enhances the healing process.
Research in the early 1990s using MRS indicated that glucogenesis may be responsible for 64% and hepatic glycogenolysis for 36% of fuel requirements in the first 22 hours of fasting. This is a radical departure from biochemistry of the past which suggested that hepatic glycogenolysis represented 65% of fuel requirements in the first 22 hours of fasting. Scientists agree that this preliminary research necessitates further studies before any strong conclusions can be reached.
The body’s response to the lack of energy input can be divided into three stages: early fasting, fasting, and starvation. Maintaining adequate energy resources for metabolism during fasting involves several adaptations, which change as the body moves from one stage to the next. The following discussion, Tables 47.1 , 47.2 , 47.3 , 47.4 , and
Figure 47-1Energy reserve utilization during fasting.
TABLE 47-1-- Mobilizable fuel reserves in a 70 kg man