In addition to my own personal fasts, I have fasted thousands of people over the past 40 years for a wide variety of health concerns. I have also been part of a group of dedicated Hygienic Physicians who have supervised many thousands of fasting patients over more than 60 years.
Fasting is one of the most profound, yet misunderstood, therapeutic approaches in health care. The word fasting comes from the Old English faestan, which means to be strict, to have discipline. By definition, water-only fasting is the complete abstinence from all food and liquids, except water, for some extended period of time.
I’m sure you can appreciate that in our culture of gluttony and overeating, the idea of voluntarily abstaining from food-unless there is some enforced famine-may seem somewhat absurd and insane. Yet, there is an extensive body of evidence over many years, including lab studies in a variety of species and clinical observations in humans, supporting the use of water-only fasting for a wide range of health problems including obesity.
These data are consistent with the idea that throughout evolution all life forms, from bacteria to humans, have experienced periods of starvation and food deprivation alternating with periods of abundant food availability and, as a result, have evolved the ability to adapt to long periods of starvation. (1)
The loss of appetite and fasting are natural to all animals, including humans, in response to disease and stress. If you observe animals in the wild, or even your own house pets, you will notice that when they are injured or diseased, they will often retire to a quiet and comfortable place, drink water and stop the intake of all food. The loss of appetite in disease is also present in humans, but the idea of complete abstinence from food for most people in our culture is such an abhorrent frightening notion that they will continue to eat even when all their natural instincts are telling them to stop. However, it is important to realize that when less energy is required for eating, digesting and procuring food, more energy is available for healing and repair.
Where Does Energy Come From During Fasting?
The body has a deep-rooted need for energy and the sugar in plants that provide it. Because sugar (glucose) is needed to produce energy in the body, the food we eat must replenish and maintain adequate blood sugar levels.
However, since elevated blood sugar levels can be dangerous, it is critical that blood sugar is maintained in a well-defined range of normal. If you over eat sugar and processed foods, sugar levels in the blood can increase to toxic levels beyond the normal needs of the body. The body protects itself by removing excess sugar from the bloodstream and storing it in the liver and muscles as glycogen for a future time of need.
If you consume more sugar than the bloodstream can handle, and the liver and muscles can accept, the surplus will be moved by the body into fat cells for long term energy storage, contributing to fat and weight gain.
When you stop eating, blood sugar levels drop. As a result, the body begins to access the glycogen that is stored in the liver, to replenish the declining blood sugar level. However, the glycogen reserve in the liver is typically depleted within the first 24 hours of fasting, and if you continue to fast, the body needs to find some way to satisfy its blood sugar and energy needs. Therefore, by the second day of fasting the amino acids from protein in our muscles, and glycerol from the fat in our fat cells are used to create sugar.
This process of creating sugar from protein and fat is called gluconeogenesis, gluco (glucose), neo (new), genesis (creation), the creation of new forms of sugar from other existing nutrients. By the third day of fasting, the metabolism of the building blocks of fat (fatty acids) from body fat becomes a dominant source of energy for the needs of the brain and body thereby conserving and sparing protein. (2, 3, 4) .
Some scientists estimate that a person between 150-160 pounds can obtain basal caloric requirements from their fat reserves for up to 2-3 months of fasting. (5)
Unscientific Fears and Concerns
Due to the use of proteins and fats in the fasting state, some people have expressed concerns about the efficacy and risks of fasting.
One of these concerns is that protein muscle mass will be so depleted on a fast leading to dangerous muscle wasting. While there is more protein metabolism and lean muscle breakdown in the first few days of fasting, about 2-3 ounces of protein loss per day, after approximately 2-3 days of fasting protein loss slows down to about 1/2-1 ounce per day to provide for a still small ongoing need for glucose. But by the third day of fasting the body shifts primarily to fat metabolism for its primary energy needs, so that by day ten of fasting the energy needs of the body are derived almost exclusively from fat.
Furthermore, the loss of protein and the depletion of blood sugar throughout a fast are more comfortably regulated by ensuring that the fasting person maintains maximum rest. If the person attempts too much activity on a fast, there will be more rapid and consistent muscle loss, as the body breaks down muscle mass to replenish blood sugar levels, and a can lead to a more potentially dangerous drop in blood sugar.
The metabolism of fat during the fasting state has generated another cloud of controversy that is unfounded and must be addressed. When fat is broken down to produce energy, a class of compounds called ketones are produced. This creates an acidic state in the body called ketosis, or a more complicated condition called ketoacidosis, and is generated whenever there is a significant breakdown of fat for energy, in lieu of carbohydrates and protein.
The concern is that ketosis in fasting could damage the kidney and brain, possibly leading to loss of consciousness and even more dire consequences. However, both scientific studies and the extensive clinical experience of hygienic physicians like myself, have shown these concerns to be unfounded.
In fact, when fasting is done in a supportive environment, with proper hydration under total resting conditions, just the opposite is observed.
Kidney and heart function often dramatically improve as weight and blood pressure drop. In an extensive study of hypertension (high blood pressure), medically supervised water-only fasts, averaging 10- 11 days, significantly lowered both systolic and diastolic blood pressure, enabling people to eliminate the need for blood pressure medication. (6)
Rather than a loss of consciousness, there is often a dramatic improvement in the acuity of special senses: vision, hearing etc. People wearing glasses will sometimes remark how they experience moments of absolutely perfect eyesight without their glasses.
In addition, in the fasting state the brain makes a unique adjustment that insures its stability even in the absence of food intake. Brain cells are one of two directly glucose dependent cells of the body.
Since the brain is truly the conductor of our remarkable body-mind symphony, the energy needs of the brain are top priority. Especially when you consider that the brain is only 2 percent of our body weight but demands 20 percent of our daily energy requirement.
However, even though glucose is essential to the function of the brain, in the fasting state brain cells are capable of utilizing ketones directly for energy in the absence of available glucose.
It has been suggested that the ketone, beta- hydroxbutyrate, is the most abundant ketone used by the brain during fasting, accounting for roughly 2/3 of the brain’s fuel supply, (7) and the ability of the brain to utilize this ketone body has permitted man to survive prolonged periods of starvation. (8)
This ability is unique to healthy brain cells and also explains how the brain and body can thrive during extensive periods of fasting. I have supervised fasts as long as 2-6 weeks for certain pathological conditions, and it is remarkable that while there is fatigue and an increased need for rest, a person is still remarkably stable in body and mind.
An interesting observation is that when brain cells become cancerous, they lose the ability to utilize ketones for energy. So that when people with brain cancer are maintained on sugar free diets, or even more powerfully, water only fasting, cancer cells and tumors in the brain may be starved, shrunk and destroyed to some degree.
Detoxification and Elimination
Fat is not only an available energy reserve in the body, but it also serves as vehicle for the storage of metabolic waste products, toxic fat-soluble chemicals and environmental toxins that we are routinely exposed to.
When fat is being utilized in fasting, the toxic debris stored in fat tissue will also be mobilized from these cells back into general circulation. This makes the toxic load of the body ripe for removal. Here’s where fasting exerts a profound benefit.
Since fasting is an energy conservation process, and energy is not being used in the procurement, digestion, and utilization of food, the energy that is harbored in the fasting process can be diverted to enhance the mobilization and elimination of waste. This mobilization of waste from storage areas, and the circulation and removal of this waste through organs and tissues of elimination, is what is more accurately referred to as detoxification and elimination.
It is important to recognize that the body in its wisdom clearly recognizes what belongs in it and what does not. It will do anything in its power to eliminate any and all threats to its integrity. This work requires energy.
When energy is made available in the fasting process, the body elaborates the action necessary, under the direction of its own innate intelligence, to carry out the inborn genetic directive of health and healing. In fasting, not only are the processes of detoxification and elimination enhanced, but the body also demonstrates an intelligent and very selective control over these processes.
So that during fasting the body will utilize what it needs least to provide support for what it needs most. It needs vital organs like heart, lungs, kidneys, bowels etc., but it doesn’t need cysts, tumors, stones, and growths. So as the body shifts from a growth mode to a maintenance and repair mode, through the process of autophagy (self- digestion), it will break down a tumor or a cyst and the debris in our cells, take from it what it can use to support the vital organs of the body and eliminate the rest.
That’s why we often see cysts, tumors, and stones break down and dissolve during fasting. As fasting is prolonged this autophagic process is also an additional attempt to produce a small amount of glucose from these extraneous tissues and conserve and spare protein muscle mass in the process.
I have monitored women with uterine fibroids or ovarian cysts that significantly shrink and dissolve after several weeks of fasting. Some of these changes can sometimes occur in relatively short periods of fasting. I had a woman come to me with fibrocystic breasts that looked like they were full of shrapnel on a mammogram. After just 7 days of fasting, the breasts were virtually clear!
(1) Lee C and Longo VD. Fasting vs dietary restriction in cellular protection and cancer treatment: from model organisms to patients. Oncogene 2011, 30:3305-3316.
(2) Cahill Jr GF. Starvation in man. N Engl J Med 1970, 282:668-675.
(3) Cahill Jr GF. Fuel Metabolism in Starvation. Annu Rev Nutr 2006, 26:1- 22.
(4) Cahill Jr GF et al. Metabolic adaptation to prolonged starvation in man. Nord Med 1970, 83:89.
(5) Saudek CD and Felig P. The metabolic events of starvation. Am J Med 1976, 60:117-126.
(6) Goldhamer A et al. Medically supervised water-only fasting in the treatment of hypertension. J Manipulative Physiol Ther 2001, June; 24(5):335-339.
(7) Cahill Jr GF. Fuel metabolism in starvation. Annu Rev Nutr 2006, 26:1- 22.
(9) Kerndt PR et al. Fasting: the history, physiology and complications. West J Med 1982, 137:379-399