Remember: 1 kg of fat is around 7700 kcal. So, for example, even if you eat 1200 instead of 200, you are still 'on track' , you didn't 'fail' and there's no need to binge. You'd need to eat ~10k kcal in 1 day in order gain 1 kg, so the weight gain that you see after a bad day is not fat.
