Table 1.

Types of intermittent fasting reported in clinical trials

	Cycle Length	Description
Alternate-day fasting	2 days	Ad libitum intake on day 1, no caloric intake on day 2
Alternate-day modified fasting	2 days	Ad libitum intake on day 1, ∼25% of daily energy requirement on day 2
Periodic fasting	1 wk	Ad libitum eating days mixed with calorie-restricted days, e.g., 5:2 with 5 ad libitum eating days and 2 calorie-restricted days/week. Restricted days can be consecutive or nonconsecutive and vary from 0 to 25% of daily energy requirements.
Time-restricted eating	1 day	Caloric intake permitted only within a defined 4- to 12-h window each day.