For thousands of years humans have practiced a wide variety of fasts. Fasting is a part of many spiritual and religious traditions and, especially recently, has been researched and used for its health benefits.
Fasting can refer to avoiding one or more types of food, limiting one's overall food consumption, or abstaining from food entirely. Fasting for health generally includes drinking water and sometimes other liquids.
The health reported health benefits from fasting are extremely wide ranging and in many cases dramatic. The main theory behind fasting's healing effects is that it causes the body to enter a metabolic self-healing state where unhealthy cells are repaired or recycled. It can also help eliminate the excess body fat associated with many health issues.
People fast anywhere from 12 hours to, in vary extreme cases, over a year. Extended fasting can be dangerous for people with certain health conditions or on certain medications and, even for healthy people, it is generally not recommended to fast for more than five days without medical supervision.
Eating all ones food within a limited window of time each day, know as "time restricted feeding" or "intermittent fasting" has also shown positive health effects, especially if the time window is early in the day.