Table 1.

Types of intermittent fasting and description.

Type of fast	Description
Alternate-day fasting (ADF)	A circular diet requires fasting for a day (consumption of no calories) and then eating freely for a day (1).
Alternate-modified-day fasting (AMDF)	A circular feeding pattern that requires fasting (consumption of 20–25% of energy needs) for a day, and then eating freely for a day; the popular 5:2 diet includes a discontinuous strict energy limit of 2 days a week and 5 other days of random eating (16, 17).
Time-restricted feeding (TRF)	Complete fast (no calories) for at least 12 h a day, and eating freely the rest of the time; the 16:8 fasting pattern currently prevails (9, 16, 18).
Periodic fasting (PF)	A circular weekly eating pattern that consists of fasting 1 to 2 days a week (burning 25% or less of the calories required) and eating freely the rest of the week on a 6:1 or 5:2 scale (9).
Common religious fasts	These include: 1. The Islamic Ramadan fast: during the 30-day fasting holy month of Ramadan, worshippers fast from sunrise to sunset and eat freely after sunset (19). 2. Greek Orthodox fasts: During fasting, people fast dairy products, eggs, and meat for 40 days (20). 3. Daniel fast: This is a biblical fast, usually for 10–40 days (20). 4. Jewish fast: one of the major fasts in the Jewish calendar is the Yom Kippur fast (19).