One nice indulgent meal or treat per weekend is acceptable, but if you're in the habit of trying to squeeze in all your forbidden foods on these two days because you were "good" all week, you've got the wrong idea. You can easily eat enough calories in two days to sabotage all the ones you saved earlier and possibly even take in extra, which will inevitably lead to weight gain. Practice the 80/20 rule: 80% of the time you eat well, and 20% of the time you indulge. Multiply those percentages by the number of meals you eat a week, and that will tell you how many "cheat" meals you can enjoy.