http://www.copperjoint.com/guide-to-intermittent-fasting-what-are-the-pros-and-cons/

Intermittent Fasting (IF) is not just about restricting calorie intake. It is about limiting your eating windows to only a few hours a day. You can fast from 14 hours to 36 hours depending on the type of IF that you do. The rationale is to eat as much as you can during your “feeding window” and not to drink or eat anything with calories during your fasting period. The goal is to reach the daily required macronutrients without restricting yourself.