Eat a low amount of calories for 4-5 days per week, from Sunday-Thursday or Monday-Thursday. This means that you should eat 12-13x your bodyweight in calories. Don't go below 12x; ignore advice that says to eat 10x because this can lead to lower testosterone levels, slow metabolism, and high catabolism (breaking down of muscle tissue).
Ex: A 170lb person would eat about 2100 calories daily from Sunday through Thursday.