Intermittent fasting can be done in a number of ways. While the 16/8 model is the most frequent and easiest to implement, other versions include the 5/2 model, which calls for calorie restriction twice a week, and the alternate-day model, which calls for calorie restriction every other day. Currently, data is unclear as to whether one type is more healthy than another, so try out several ways to find which one works best for your body and lifestyle.