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Fasting is going without food entirely, abstaining from certain types of food (often meat), or reducing food intake drastically (such as a juice-only diet), for a specified period of time.
Fasting is usually done for several reasons:
Fasting is calorie-cutting in its simplest form. Practiced as a crash fad diet, fasting is ineffective in the long term, as weight lost during the fast will be gained back upon resuming an unhealthy diet. Intermittent fasting, such as eating only one or two meals a day, or eating less on certain days, can be effective if continued indefinitely, and may be easier to adhere to than continuous caloric restriction. As with any diet, it is most effective when combined with exercise.
Fasting (called more appropriately, a "hunger strike") has also become one of the few ways for prisoners without other resources (like lawyers, human rights workers, guards, etc.) to protest the conditions they are being held under. Historically used by Gandhi, IRA members Terence MacSwiney and Bobby Sands, British suffragettes, the prisoners at Guantanamo Bay, and most recently, Wal-Mart employees protesting low wages.
Virtually every religion has some aspect of fasting, though the specific rituals and purposes vary depending on the religion.
Muslims typically fast during the month of Ramadan, typically to learn self-restraint (Taqwaa).While fasting from early daylight (not dawn) until sunset, Muslims refrain from consuming food, drinking liquids, smoking, and engaging in sexual relations. For more, see the main article.
Christians fast for a variety of reasons including spiritual purity, spiritual focus, gratitude and reminder of the sacrifice of Jesus. Anorexia mirabilis (meaning "miraculous lack of appetite") is/was the practice of starving oneself almost unto death, common in the Middle Ages. It is sometimes practiced as part of spiritual warfare, or as part of an exorcism. Many Christians, mostly Roman Catholic, fast during Lent, 40 days before Easter (It is actually 46 days but many traditions exclude Sundays from the requirement to fast.).
In 600 CE, Pope Gregory I declared that fetal rabbits were aquatic and therefore "fish", which could be eaten during Lent; his declaration marked the beginning of rabbit domestication. By around 920 CE, Christians began giving up red meat on fasting days for fish and foul. This marked the beginning of breeding chickens to lay eggs all year-round.
The most famous Jewish fast day is Yom Kippur the day of Atonement. It is biblically mandated and is the one fast that most Jews are both aware of and actually participate in, taking place from sundown the night before to sundown the night of Tisha B'Av, which commemorates the destruction of the Jewish temple and additional tragedies which befell the Jewish people. There are also several minor fast days dotted throughout the liturgical calendar and many couples, prior to their wedding, will also fast.
Fasting is also found in a host of Native or spiritualistic religions, including such popularized activities as the "vision quest", in which one goes without food for three days in a wilderness setting while they reflect on the meaning of life, search for guidance, or honor their tribe and world.
While fasting may have some health benefits, it is easily pushed into the area of woo. Fasting is claimed by its proponents to cure all manner of diseases and ailments, up to and including cancer, and give the body a chance to cleanse itself of toxins.
The changes that happen in the body during a fast depend on the length of the continuous fast. The body enters into a fasting state eight hours or so after the last meal, when the gut finishes absorbing nutrients from the food.
In the normal state, body glucose, which is stored in the liver and muscles, is the body’s main source of energy. During a fast, this store of glucose is used up first to provide energy. Later in the fast, once the glucose runs out, fat becomes the next source of energy for the body. With a prolonged fast of many days or weeks, the body starts using protein for energy.This is the technical description of what is commonly known as "starvation". It is clearly unhealthy and involves protein being released by the breakdown of muscle, which is why people who starve look very thin and become extremely weak.
Several studies on intermittent fasting have suggested health benefits such as reduced inflammation, and improved insulin sensitivity and tissue repair. One study found a multi-day fasting regimen greatly improved blood pressure.
Fasting for a short period is recommended prior to receiving certain blood tests, or before performing a colonoscopy endoscopy, or prior to surgery involving general anesthesia (to reduce the risk of choking on one's breakfast).
- DNA evidence is rewriting domestication origin stories: Fresh ideas emerge about the origins of humans’ relationships with their favorite species by Tina Hesman Saey (12:00pm, July 6, 2017) Science News.