There is no one standard way to practice IF. “Intermittent fasting is an umbrella term for three different types of diets,” says Krista Varady, PhD, a professor of nutrition at the University of Illinois in Chicago and a researcher on intermittent fasting. Here’s what you’re most likely to see, she says:
Alternate-Day Fasting
For the most common type of alternate-day fasting, you eat 500 calories every other day. On off days, you can eat what you want.
5:2 Diet
Popular in the United Kingdom, you consume 500 calories on two nonconsecutive days per week. On the other days, you eat whatever you like.