This is an old post I realize. Are you still doing 5:2? I did it last year and I plan to start back up in preparation for the holidays.
I do best when I skip breakfast (but I still have coffee), then I eat chicken breast or salmon with steamed vegetables for both lunch and dinner. I get low blood sugar and jittery when I don't eat so I was nervous to start this but once I did I felt fine. I think it was the fact that most of my 500 calories was coming from protein instead of carbs.