Many people may also fast as part of a medical procedure or a check-up, such as preceding a colonoscopy or surgery, or prior to certain medical tests. Metabolic changes of the fasting state begin after absorption of a meal (typically 3–5 hours after eating).Ī diagnostic fast refers to prolonged fasting from 1 to 100 hours (depending on age) conducted under observation to facilitate the investigation of a health complication, usually hypoglycemia. For example, a person is assumed to be fasting once 8–12 hours have elapsed since the last meal. Some diagnostic tests are used to determine a fasting state. Several metabolic adjustments occur during fasting. From a purely physiological context, 'fasting' may refer to the metabolic status of a person who has not eaten overnight (see the ' Breakfast'), or to the metabolic state achieved after complete digestion and absorption of a meal.
JSTOR ( February 2016) ( Learn how and when to remove this template message)įasting is the willful refrainment from eating and sometimes drinking (see Water fasting and Juice fasting).
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