During a fast, a person purposely abstains from food for a specific period of time. Fasting
has been practiced throughout the ages for both religious and therapeutic purposes. A one-day
fast is unlikely to cause any harm to a healthy body. Slightly longer fasts (two to three
days) are also well-tolerated by most healthy people.
No matter how short the duration, fasting is unwise and potentially dangerous for some
people, including pregnant and lactating
women, people with cancer, diabetes,
gout, hypoglycemia, stomach ulcers, liver, kidney, or lung disease, or
anyone with a compromised immune system. Some
health experts caution against fasts lasting more than two to three days, even for healthy
individuals—if longer fasts are practiced, they should be medically supervised.
During the first 24 hours of a fast, the body is able to utilize its stored
carbohydrates—in the form of glycogen—to fuel essential body processes. When
glycogen reserves are depleted, fat becomes the preferred energy source, so that protein
(e.g., as found in muscle tissue) is partially spared.
However, some muscle tissue is often lost, even during short fasts. Weakness, nausea,
headaches, and depression can also develop during a fast, because ammonia and nitrogen are
released into the blood during the breakdown of muscle tissue. Ketones, byproducts of fat
metabolism, are produced once the body switches from burning carbohydrates to burning fat.
Elimination of ketones is accomplished by the kidneys. In extreme cases, extended fasts can
lead to disturbances of heart rhythm and death.
“Modified” fasts, in which fruit or vegetable juices and herbal teas are consumed, are probably easier on the body
than all-water fasts. Even so, a modified fast should be limited in duration; modified fasts
lasting more than a week should be supervised by a healthcare professional.
Why do people follow this diet?
Proponents claim that environmental toxins build up in our bodies over time and need to be
removed periodically through fasting to maintain optimum health. Cleansing fasts are an
important part of a detoxification program and may be part of a weight-loss program.
What do the advocates say?
Advocates believe that fasting periodically gives the body a break from digestion and
allows it to eliminate the toxins that cause disease, while promoting healing and reversing
the aging process. Studies indicate that fasting helps health conditions such as rheumatoid arthritis, migraine headache, and skin diseases. Acute illnesses
such as colds and flu, colon disorders, allergies, obesity, and respiratory diseases may also respond to
fasting. Proponents claim a one-day fast creates a clearer mental state and increased energy.
They believe a three-day fast rids the body of toxins and purifies the blood, and that a
long-term fast promotes healing, alleviates food allergies, sheds pounds, and rebuilds the
immune system.
What do the critics say?
Critics believe that fasting depletes the body of important nutrients, essential minerals
and energy, may be unsafe, and is an ineffective weight loss aid. The few pounds that are lost
in the beginning of a fast are from water, and this weight will return as soon as the fast is
over. Few scientific studies have been done to back up health claims and demonstrate that
fasting works by releasing toxins stored in fat.
Are there any groups or books associated with this diet?
International Association of Professional Hygienists
4620 Euclid Boulevard
Youngstown, OH 44512
(A professional organization of doctors who specialize in therapeutic fasting. Write to them
for a list of certified members.)
Fasting and Eating for Health: A Medical Doctor’s Program
for Conquering Disease, by Joel Fuhrman, MD, New York: St. Martin’s
Griffin, 1998.
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