I always make sure I eat properly before a gig. The timetable often works like this:

6.30pm - set off for gig
7.00pm - get to gig, set up and sound check
8.00pm - start playing for dancing
9.20pm - break
9.40pm - resume playing for dancing
11.00pm - finish gig and clear up
11.30pm - set off for home
12.00am - get home

With the food on offer during a break varying from none to a buffet, I take no chances and make sure I have a meal before I set off. I also take a Mars bar or similar in case of low blood sugar. There's no way I'll eat at midnight.

Everyone's different.