You should have at least 2 days off a week to let your body rest and recover. On your days off from working out you should still take in a good source of protein. Most people also use rest days for days that they have their cheat meal. Saving cheat meals for rest days is not a good idea, especially if you are looking to lose weight or watch your diet. My reasoning behind this is because your body is already in calorie overload and when you eat that one cheat meal it will maximize your calories without doing any physical activity to burn the calories off. If you are one of these people who are set in your ways and have cheat meals on your day off I would suggest you eat that cheat meal for lunch and then do 30-40 minutes of cardio after, but then again your really not giving your body a break. Typically I save my cheat meals the day before my leg day. I do this because your body needs plenty of energy for leg day. The day before is best to carb overload, it can take up to 18 hours for carbs to fully digest and disperse into your body for maximum energy.