Fasting
Fasting is the practice of abstaining from food and beverages, often for a defined period, and has been a part of various cultures and religions for thousands of years. It is commonly undertaken for religious reasons, medical procedures, or dietary goals. Religiously, fasting is observed in many faiths, such as Judaism, Christianity, and Islam, each with unique guidelines about when and how to fast. For instance, Jews fast on Yom Kippur from sundown to sundown, while Muslims observe fasting during Ramadan, breaking their fast at sunset with a communal meal called iftar.
In a medical context, fasting is often required before certain procedures or tests to ensure accurate results. Common medical advice typically advises fasting for six to twelve hours prior to blood tests to avoid nutrient interference. On the dietary side, techniques like intermittent fasting are popular, where individuals cycle between periods of eating and fasting. This approach includes methods such as the 16/8 method, where one fasts for 16 hours and eats within an 8-hour window, and the 5:2 diet, which allows normal eating five days a week while restricting calories on two non-consecutive days. While some studies suggest potential health benefits from intermittent fasting, it is crucial for certain individuals, like those with diabetes or specific health conditions, to consult healthcare professionals before starting any fasting regimen.
Subject Terms
Fasting
Fasting is the act of abstaining from food and drinks (and sometimes other activities) for a specified period. It has been practiced for thousands of years and for a variety of purposes. Most people fast for religious reasons, medical procedures, and dietary purposes.
Fasting for Religion
Fasting is a required practice for followers of many religions such as Judaism, Christianity, and Islam. People fast as part of a particular religion as a sign of sacrifice. The parameters surrounding fasting typically differ by religion. Some religions prescribe certain days and times to fast. Some allow certain foods to be consumed, while others do not allow followers to consume anything during the fast.
In Judaism, the rules for fasting are very strict. Followers fast and pray on several religious days, such as Yom Kippur—considered the holiest day of the year—from sundown to sundown. The day is focused on forgiveness. Followers abstain from all food and drink (even water) during fasts. In addition to religious days, Jews sometimes fast in times of trouble.
Traditions surrounding fasting in Christianity have changed over time. Because the Bible does not mandate fasting, Christians do not follow this practice as closely. Christians typically fast by reducing meals and abstaining from meat on Fridays during Lent, a period of six weeks before Easter. In addition, some Christians give up something of their choosing such as eating sweets, drinking alcohol, or smoking during Lent. Christians also may fast on saints' feast days and other holy days.
Muslims, who are followers of Islam, follow strict fast rules. Followers fast during the day (sunup to sundown) during the holy month of Ramadan. Once the sun goes down, the fast ends with a meal known as iftar. Muslims typically fast and end the fast together as a community. Muslims also may fast on other Islamic holy days, and sometimes these fasts include restrictions on other activities such as smoking. Not all Muslims practice fasting in the same way, however. Some interpret the Quran to mean they should feed the poor instead of fasting.
Other religions practice fasting but do not follow strict rules. Buddhist monks and nuns abstain from food and other activities at varying times. Followers of Hinduism fast on different days according to the deities worshiped. Mormons, who are followers of the Church of Jesus Christ of Latter-day Saints, fast during two meals on the first Sunday of every month. Then they donate the money they would have spent for these meals to the poor. This is similar to the way some Muslims view fasting.
Fasting for Medical Procedures
Many medical procedures, such as blood tests, require patients to fast for about six to twelve hours prior to receiving them—depending on the type of test. Some common blood tests check the levels of glucose (sugar), iron, and cholesterol (lipids) to help diagnose diseases or conditions.
Before a medical test, a person should avoid eating foods or drinking liquids (other than water) for a specified amount of time. Patients typically are allowed to drink water before certain medical procedures because water keeps the veins hydrated, making it easier to draw blood. When a person consumes foods and beverages, nutrients from these are absorbed into the blood. Nutrients can alter the results of certain tests and give inaccurate results.
Patients should continue to take any vital medications during the fast unless directed by the physician. They should check with the physician about taking vitamins and supplements, however. Patients also should not smoke when fasting. After the test is over, a person should eat or drink something as soon as possible. This prevents dizziness, fatigue, and hypoglycemia (low blood sugar) caused by not eating for a long period.
Fasting for Diet
Fasting for diet-related reasons is different from fasting for other purposes. A person cannot go without food or water for very long, as this will have a detrimental effect on the body. Abstaining from food for long periods is very unhealthy. The type of fasting used for dietary purposes is called intermittent fasting. Intermittent fasting is a method of eating in which a person goes through cycles of fasting and cycles of eating. Several types of intermittent fasting programs exist, but they mostly follow the same pattern: times of eating and times of fasting.
The typical person fasts every night when sleeping, so intermittent fasting can be thought of as extending this fast. A person can wait to eat until a few hours after he or she wakes up, or by skipping breakfast. During this fast, known as the 16/8 method, or Leangains method, a person fasts about sixteen hours and eats during an eight-hour period. Fitness expert Martin Berkhan created this fast. During the fast time, a person can consume water, coffee, tea, and other non-caloric beverages.
On the 5:2 fast, a person eats normally five days a week and eats about five hundred or six hundred calories two days a week. British journalist and doctor Michael Mosley popularized this method of fasting. During fast days, a person typically eats two meals of about 250 to 300 calories each.
The eat-stop-eat method from fitness expert Brad Pilon involves a full day fast one or two times a week. A person fasts from one meal one day to that same meal the next day, such as from lunch to lunch or dinner to dinner. For example, a person on this fast eats dinner one night and then does not eat anything else until the same time the following night.
During alternate-day fasting, a person fasts every other day. During fast days, a person can either consume no food at all or five hundred calories of foods.
The Warrior Diet from fitness expert Ori Hofmekler involves eating one large meal at night. A person fasts all day and then eats once at night. During the fast time, a person can eat small portions of raw fruits and vegetables. The large meal should only include healthy, unprocessed foods.
Some researchers believe there may be a potential health benefit to intermittent fasting, which has the potential to rest the liver, spleen, and kidneys from their job of daily elimination of toxins in food, but there is no conclusive evidence that fasting improves one's metabolic profile better than other diet strategies to lose weight and lower risk of cardiovascular disease. Some people should not attempt fasting if they have diabetes, or are being treated with drugs for blood pressure or heart disease. Additionally, research has shown that intermittent fasting may not be beneficial for females and may lead to menstruation disruptions and other harmful effects.
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