Hello summer2008melanie and welcome to your new WOL with fasting.

Lots of the questions that newcomers have are answered here: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

The 500kcals is recommended as the kcal intake for women on a fast day. On a non-fast day, you eat to your TDEE (as explained in the above thread).

I hope that you find out quickly whether IF/5:2 or whatever pattern of fasting you adopt is a good match to your life and that it helps you to meet your health and other goals.

Good Luck.

IMO it is worth reading the book, before embarking on this way of eating, or read it as soon to starting as possible.

I’ve noticed that a lot of people have taken the phrase “on non fast days eat what you like” literally and come unstuck.
It means that no foods are restricted, NOT eat as much as you can of anything you can get your hands on! So if you want a burger that is fine, but don’t have cake and ice cream too, save them for another day.
It is really important to find out what your BMR and TDEE are. TDEE is what you should eat for someone of your sex, age, weight and activity level, so you should aim not to exceed that on non fast days. BMR is how many calories you can eat if you sit on the sofa all day and do nothing.

If you take a look at the other threads you’ll see that there are many ways of following this eating plan. That is the beauty of it as you can tailor it to fit your lifestyle. It isn’t a quick fix, but it works and the most important thing it does is help you to change the way you think about food, and your eating habits. There are many contributors who like me, have been on numerous diets over the years, but have always regained the weight and more because they haven’t changed their eating habits.
This is the way forward 🙂

Good luck.