I've started the 5:2. 5 days, I do like you, but make sure I get in the normal 1700-2000 calories, then on the other two days, I just do 1 meal of 500-600 calories.
The key is to not do the same thing every day, so that your body doesn't adjust to it, eat at different times of the day, and vary the calories from day-to-day.
Interesting, will keep that in mind.
I also try to do some light exercise (bench press, uphill walking/treadmill) Mon-Fri as the last thing I do in the late morning before my first meal.