Is Fasting Healthy or Dangerous?

Millions of people all over the world take part in various forms of dietary fasting. For some, that means the total elimination of solid and liquid foods from the diet for a specified period of time. There are, however, endless variations on the definition of the term “fasting.”

And there is a long list of reasons for fasting as well. Some people do so with the aim of improving their mental or physical health, while others use fasts as a way to treat diseases. Aside from physical aspects of fasting, there is also a political angle to the practice; throughout history, people have fasted to bring attention to a cause, as a protest against unjust laws or leaders, or just to attract media attention to personal plights.

Regardless of the reason for taking up a fast, the big question looms: is fasting good or bad for the human body’s overall health? Those who fast for political or religious reasons don’t concern themselves with this query; but for the hordes of modern-day fitness buffs who fast to gain stamina, lose weight, “purify” the body or improve the general state of their health, this question is an urgent one.

What is fasting, and why do people do it?

Loosely defined, fasting is the total or partial restriction of any food or liquid that is normally consumed during the course of a typical day. People have been known to eliminate all sorts of things from their diets for long or short time periods.

There are water fasts, which allow only the intake of water, meat fasts, which allow everything except meat, and so-called “dry” fasts, which cut out all food and drink. Many fasts are named for the item that is eliminated, like alcohol, meat or sugar fasts. Others are named for what can be eaten, like fruit-and-vegetable fasts and the above-mentioned water fasts.

In modern times, the huge majority of fasting is done for health reasons, but there are many who still take part in regular bouts of religious fasting. Catholics, Buddhists, Muslims, Hindus, Jews and other religious adherents regularly eliminate certain kinds of food and drink from their diets during religious holidays or in times of mourning. The Bible, for example, specifically lists numerous kinds of fasts and explains the reasons for undergoing the sometimes strict regimens.

Doctors often put their patients on short-term fasts for diagnostic tests that can only be performed after the digestion of food. Still other medical professionals have their clients fast either intermittently or long-term as a way to treat various ailments, to boost immunity or to decrease the negative effects of chemotherapy.

Patients scheduled for surgery are often instructed to restrict their intake of solid food for as much as 72 hours before a procedure, especially if general anesthetics are to be used during the operation. Finally, psychiatrists have discovered that intermittent fasting can decrease the severity of depression in some cases.

There are so many kinds of fasting it is difficult to say outright whether the practice itself is good or bad. When instructed by a physician to fast before surgery, or when eliminating meat from the diet for a few days during a religious holiday, fasting is usually safe and effective for its intended purpose. Unfortunately, more restrictive, voluntary fasts that are something of a modern fad are often risky, and sometimes quite dangerous.

Which fasts are safe, and which ones are dangerous?

Is fasting a smart way to lose weight or cleanse the body? The medical literature has quite a lot to say about the practice. Millions of dollars have been spent studying the pros and cons of fasting, and the results are mixed. In the majority of cases, the longer and more restrictive a fast, the less medical benefit it has. Here are some key points to keep in mind about weight-loss and curative fasts:

• People fast to lose weight, “cleanse” their bodies, fight disease, and to prolong life. Whether fasting actually achieves these goals is the subject of much debate and research.
• Human beings have been fasting for at least 3,000 years, either for religious or health reasons, or both.
• Most medical studies show that fasting is not a smart way to lose weight. It might be quick and relatively easy to fast away 10 or 20 pounds, but that weight usually comes back in a few weeks. In fact, some research has shown that weight-loss fasts end up causing a person to gain pounds in the long-run.
• Weight-loss fasts can be dangerous, in addition to being ineffective. People who are taking any kind of medication, who have immune system problems, or who have liver ailments can do a lot of damage to their bodies by fasting. Some doctors think fasting for weight loss is one of the most destructive and misguided things a person can do. Rather than losing weight sensibly and healthfully by eliminating bad eating habits, fasting offers the illusion of a quick fix.
• Combining fasting with practices like colon cleansing and enemas can be downright dangerous, according to experts. Because the intestinal tract contains both good and bad substances, extreme cleanses can get rid of the good stuff along with the bad, leaving the body in a real mess.
• Experts are nearly unanimous in their belief that “detox” fasts are not effective. The human liver is a detoxification center for the body, and it gets plenty of help from the skin, colon, lungs and kidneys. When the body is unable to eliminate toxic substances, the reason is almost always a diet that is nutrient-poor. Artificially eliminating weight, by fasting, and getting rid of toxins, by cleansing, is a dangerous one-two punch for an otherwise healthy person.
• Nearly every “toxin” in the body is a result of processed foods and low-nutrient foods that make up just over 50 percent of the modern American diet. Eliminating processed foods, exercising regularly, and getting regular checkups are the keys to natural detoxification, experts believe. The answer is not in cleanses and weight-loss fasting.
• There is a body of medical evidence that goes at least partially counter to the standard anti-fasting dogma. Because short fasts are a natural process (the word “breakfast” is based on this concept), some medical professionals and researchers believe that intermittent fasting is a good way to eliminate some of the unnatural waste buildup from processed foods. Anyone who wants to undertake an intermittent fast should discuss the procedure with their health care professional. It is never a good idea to embark on a new dietary or exercise regimen without clearance from a trained professional.
• Fasting under the supervision of a doctor has been shown to treat physical and mental ailments like depression, psoriasis, lupus, heart disease, colitis, arthritis and other conditions. Experts who recommend this kind of fasting note that a healthy diet before and after the fast is essential for success.

Notes of caution

Some people should be especially careful even with short bouts of fasting. For example, most doctors recommend that pregnant women should not fast at all. This advice is also given to anyone with kidney or heart problems.

Fasting does have some advocates, but even pro-fasting medical experts point out that it is always wise to get a doctor’s approval first, maintain a healthy diet before and after the fast, and not stay on the fast for more than the recommended time (usually not more than several days, depending on the specific program).

It seems pretty clear, however, that fasting for weight loss is not a wise way to approach any kind of a weight problem. For longer life and better health, the general consensus of the medical community seems to indicate a well-balanced diet, moderate exercise and a positive mental attitude.