Cheat Day Science!
There is a lot of differing opinions regarding both the actual concept of the 'Cheat Day,' and exactly how effective/useful it is in the context of achieving fitness results through dieting and training. However, irrespective of whether or not it will help you achieve your results faster or indeed if at all - let us first discuss what the 'Cheat Day' and/or 'Cheat Meal' is in the eyes of those who use it:
THE CHEAT DAY
Typical Use: All macro-nutrient ratios on a diet plan are ignored for the entire day, and the trainee eats what they want to eat at any time they want, without recording any nutrients or calorie amounts. The Frequency of the Cheat Day is usually at most one day per week.
THE CHEAT MEAL
Typical Use: All macro-nutrient ratios on a diet plan are ignored for one meal, and the trainee eats what they want to eat, without recording any nutrients or calorie amounts. The frequency of the Cheat Meal is usually one to two times per week (instead of one big Cheat Day).
NOTE: The 'Cheat' aspect of the Cheat Meal or Day is what is important to note. When you are 'Cheating' you are not following the rules, and in this case it means you are not following the rules of what is most likely a very strict diet of a particular macro-nutrient ratios from clean sources. So this means that a 'Cheat Meal/Day' approach is not the same as a 'Flexible Diet' or 'IIFYM' approach, where your macro-nutrients ratios are the only rules to follow, and the sources from which you eat them are less strict.