Right, here's the thing... if you don't eat today, you will never eat on a WI day again. Ever.
Don't fall into the trap of starving yourself on a WI day. There are so many of us who do.
By all means don't eat a huge meal but eat something, and eat properly. That means breakfast and lunch.
I WI at 5.30. I have a big cooked breakfast and then a light lunch of ryvita or something and fruit, or I have cereal and then a lunch of ham or chicken salad or some soup and fruit.
What you have done all week will give you a good result, not what you eat today.
Good luck.