Intermittent fasting is not a traditional diet, it is more of a specific style of eating characterized by eating during a set duration of time followed by a longer than usual fasting period. The most popular method of following intermittent fasting is called the 16-8 method, where all of the day’s calories are consumed during an eight hour window bookended by 16 hours of fasting. Other types of intermittent fasting include the 5-2 method, in which a person would eat regularly for five days of the week and consume little on two nonconsecutive days. Generally on the fast day calories will be capped at 500; this method can be successful as long as additional calories are not consumed to compensate on the non-fasting days. Another method of intermittent fasting involves normal eating patterns with longer fast periods interspersed, usually between 24 to 36 hours.
Humans evolved to be able to fast for long periods of time. Before the agricultural age began eating habits were characterized by when animals were killed or fruits and vegetables found, not by any set meal schedule. Intermittent fasting more closely replicates this style of eating than any other modern diet; it can be much more difficult to perform psychologically due to the abundance of food that is easily available in the modern world.