This food plan is not prescriptive. You can try to go all day without eating, but if you do eat, don’t go beyond 500 calories.

Typically IF Intermittent Fasting starts after sleeping. The fast is over after waking up the following day.
The 500 calories is part of a doable approach…

There is also ADF Alternate Day Fasting
For me what I found doable after getting used to 5:2 600 calorie days about the 8 week mark.
4:3 Monday, Wednesday, Friday 600 calorie days. Tuesday and Thursday were health food days.

This left weekends open I typically allowed for Saturday morning breakfast to be unrestricted. But ate fish or soups for lunch and dinner. Also ate a buffet on Sunday mostly vegetables skipping the starches , but only ate low calorie soups for rest of the day.
Although I was hungry about 9 times a week for 2-3 hours I never felt starved.
I tried to eliminate hunger altogether by eating red kidney beans for lunch and catfish for dinner.. Followed by zero calorie vitamin water to help get the full feeling.
Weeks 11- 18 i was not hungry , not even once! Lost 6 lbs over that time. 6 lbs was not alot. however I had already lost 14lbs in the first 10 weeks. Losing 20lbs in 18 weeks I kept on for 8 months losing 32lbs.

I restarted IF in march of 2014 I had kept off 27lbs from my starting weight in 2013.
I was 274 when I started in march of 2013
I’m now 230.

My opinion is the Doable approach of 600 calories 2-3 times a week , and stopped overeating except for Saturday and Sunday breakfasts.
My goal is to reach 100 lbs fat fat loss.

Typically most dieter that achieve the most weight loss are dieter the sleep a lot?
I swear I’m not making this up!

This was easy for me because as a child , I would be out on a bot with my dad . Thinking it would be almost time to eat at sundown. My old man would just throw out an anchor and go to bed. He’d wink and say something like” no fish no fry! Anyway it was just how we did things. Don’t eat and then sleep.
It’s doable. Sleep then eat!