Evening plans shouldn't interfere at all. In fact a day of fasting will do wonderful things to your insulin sensitivity which will mitigate the effects of a bit of junk if you so wanted to indulge!

The best way to do this by far is to skip breakfast and maybe lunch and have an evening meal, that way you don't go to bed hungry and you sleep better.

Nicotine gum (1/2mg) for food cravings and appetite is awesome too