Fasting is the act of abstaining from food, or from certain types of food, for a set period of time, usually for nutritional, exercise or religious purposes. In relation to diet and nutrition, usually there is a set time of fasting every day, called "intermittent fasting," used to aid in optimal weight loss and muscle development while exercising. The theory behind intermittent fasting tends to derive from the idea that pre-agricultural humans tended to have longer periods between meals, hunting or gathering for usually one large meal per day rather than the three square meals advocated today.
Fasting Due to Surgery
Most surgical procedures or blood-draw procedures require a certain time period of fasting, from 12 hours up to two weeks on liquids only. The purpose for setting up fasting rules pre-surgery is to ensure that the patient has expelled all the contents of the digestive system, but also to keep the patient from becoming overly thirsty, which could lead to dehydration. One common rule of pre-surgical fasting is the "nothing by mouth after midnight" rule, which disallows anything but water after midnight on the night before the surgery. For surgeries that deal with the digestive tract or organs, some surgical facilities require clear liquid diets -- broths and water -- for up to two weeks prior to surgery.
Fasting for Weight Loss
Weight-loss plans such as Eat Stop Eat have become more and more prevalent as dieters rely on intermittent fasting to help them break cravings and stop overeating. Eat Stop Eat's plan recommends that participants fast in 24-hour bursts. Rather than fasting for a full waking day, however, which would cause the dieter to fast for over 30 hours, the plan runs from 6 p.m. to 6 p.m. For example, the dieter would have dinner after 6 p.m., then breakfast and lunch the following day. On that day, the dieter would skip the dinner meal, as well as breakfast and lunch the following day, but break the fast again at 6 p.m. Proponents of fasting claim that it can decrease fat and improve muscle mass and immune functions.
Fasting for Detox
Detoxification diets, long used as ways to remove toxins from the body, often require a period of fasting from solid foods or specific types of foods for a period of time, often lasting up to two weeks. Most detox plans specify rules that restrict diet to specific raw vegetables and fruits and purified water. Some plans will also advocate for certain herbal remedies or supplements to be taken; still more recommend enemas to cleanse the colon during the detox process. MayoClinic.com's experts state that detox diets likely don't provide any lasting benefit and can cause problems such as dehydration, fatigue and dizziness.
Fasting for Religious Reasons
Rules for fasting due to a religious practice or holy day vary across religions. For example, Buddhists tend to have fast days on or around the full moon, usually denying themselves solid foods and some liquids during the fasting period. Muslims celebrating Ramadan not only fast from food during the ninth month of the Muslim calendar, but also from alcoholic beverages and other drinks, foul language and smoking from dawn until sunset each day. Catholics in the Christian religion fast from meat on Ash Wednesday and Good Friday -- celebratory days at Easter time --, and during the celebration of Lent, they fast from meat each Friday.
References
- World Federation of Societies of Anaesthesiologists; Pre-operative Fasting Guidelines; J. Roger Maltby, MB; 2000
- SB Wire; Eat Stop Eat Offers Unique Weight Loss Alternative; June, 2011
- Belief Net: Fasting Across Religions
- MayoClinic.com; Do Detox Diets Offer Any Health Benefits?; Katherine Zeratsky, R.D., L.D; 2010
