Fasting is the practice of abstaining or reducing consumption of food, drink, or both, for a specific period of time. Everyone fasts for at least some part of the day, generally the eight or so hours that one spends sleeping every night. Physiologically, fasting can refer to a person’s metabolic status after not eating overnight, or even the metabolic state after the complete digestion of a meal. Once you’ve gone eight to 12 hours without eating, the body enters a state of “fasting.”
The practice of fasting can lead to a number of metabolic changes within the body. These changes typically begin approximately three to five hours after eating, when the body enters a “post-absorptive” state – rather than the state on ongoing digestion, where eating frequent meals means the body is always involved in some sort of digestive activity.
Whether you practice more long-term fasting for health reasons or for spiritual reasons, most people will have to fast at some point for medical reasons. Patients undergoing surgery or other medical procedures that require a general anaesthetic will usually fast prior to the treatment, but fasting is also practiced before a number of other medical tests, including cholesterol testing, blood glucose measuring, or a lipid panel. This enables doctors to achieve accurate results and establish a solid baseline to inform future testing, if necessary.