Krista Varady, PhD, is an associate professor of nutrition at the University of Illinois and the world's leading researcher into alternate-day fasting. She has published more than 30 papers on the topic in prestigious journals such as The American Journal of Nutrition and Obesity, and she has discussed her breakthrough findings with consumer magazines, such as Elle and Men's Health.

A regimen in which one limits calories on Diet Days, and then eats anything one wants on Feast Days.