I've started reading the 5:2 threads this morning but there's so many posts struggling a bit to pick out the info I need! hopefully will be posting away in there soon.
I've got the book and I think 5:2 is for me, but for weight loss is anyone calorie counting in conjunction with fasting? the MFP app says I need 1200 calories per day to lose the weight I want, so should I be eating this on non fast days and 300cal on fast days? that's going by the idea of eating a quarter of your normal intake.
Ignore MFP - if you read through the very first post that's in all the 5:2 threads you will find a link to a calculator to work out your TDEE (total daily energy expenditure). That's what you're aiming for on non fasting days. Stick with the 500 on fasting days although if you want to eat less then that's fine.