In short, yes it could be best to eat all 500 calories as one meal.

See this page below, this person emailed all the scientists in the original Horizon documentary to ask the very same question you ask. Here he details their responses.

http://feedfastfeast.com/2012/08/25/grabbing-the-bullshit-by-the-horns/

I and some others on here do have all 500 calories in one go but it’s not vital. Certainly, when you’re starting out on this lifestyle, it’ll take you a while to get past the ‘hunger pangs’ stage to a point where you realise that it’s not genuine hunger and water WILL make it go away. When you’re starting out you might want to split your intake over 2 or 3 smaller ‘meals’. If you can last all day and have it in one go though, there probably are more benefits to doing it that way (a longer ‘fasting period’ will allow the IGF-1 effect to properly kick in and if you exercise during your fast it’s supposed to help with fat burning efficiency).

Hi Maradorno, experiment, find a system that works for you. As you see there are many very good and well researched comments about this subject but my advice is do what suits you.
Good luck.

gfsher – I hope you don’t mind me asking and ignore me if I’m being too intrusive. I don’t think most people like being hungry (although it’s entirely different, of course, from true hunger/starvation courtesy of famine or poverty) but I was interested to hear you say it scares you. Would you mind sharing why? I think our attitudes to food are key to losing/gaining weight. We all have our issues!

Anniann, that is really interesting, thank you. So it’s not the hunger that’s so concerning (even if it’s a bit uncomfortable), but the fear that the appetite/desire to scarf down everything in sight post-fast will undo all the good work. In that case, isn’t it brilliant that the 5:2 really seems to suppress that desire too? I know that I always expect to be ravenous the day after the fast but on waking I’m very casual about when I eat, and the hunger pangs from the night before have completely vanished. It’s normally at least 10am before I make my breakfast, by which time I’ve been awake for 3 hours or more.
The one really big mistake I’ve made is not feeling particularly hungry for supper the night before fasting and so not eating adequately pre-fast – that made the fast day so much more difficult than it normally is. Won’t be making that mistake again!

The thought of fasting or becoming ‘too hungry’ seems to scare people. I was sharing details of the The Fast Diet with co-workers over lunch and those that immediately objected thought they couldn’t do it because they would get too hungry and therefore feel weak and woozy – and this would be intolerable for them.

I have just started up on the diet again today after a couple of months break. But the most time I have managed to not eat is for 14 hours (7pm – 9am)and then having something like a raw carrot or a handful of almonds – but my aim will be to try and stretch this out gap out slowly to widen the fasting gap.

Regardless I did feel that in the few weeks that I previously did on the fast diet I did achieve some acceptable weight loss – even with low cal grazing across the day.

Very interesting thread and thanks a lot for the link!
I had my first fast day on July 31 and fast Sundays and Wednesdays – though I did Sunday, Tuesday, Sunday one week (was about to venture into AFD but decided against it at the time).
Up until yesterday I have had a large mug of tea with milk in the morning, some fruit around 1 pm, and maybe one more in the late afternoon, and finally a “large” meal of ca 300 kcal around 6 or 7 pm.
Yesterday I decided to challenge myself a bit more, so I only had oolong tea (w/o milk) and water the whole day and then all my kcal’s in one meal in the evening. To my utter surprise, the day was easier than any other fast day before! I didn’t go without calories for a full 24 hours, but close enough and on Wednesday I will.
Sunday included some heavy gardening (uprooting small trees and what have you) and a 45 minute brisk walk later on. Energy levels were great all day.
Like quite a few of those who have posted above, I was, least to say, apprehensive about going a good part of the day without anything. Brainwashed by WW and other advisors, I guess. Moreover, I was convinced I would become a very unsociable creature if I didn’t get my black tea with milk first thing in the morning.
I would now encourage anyone who managed to do 500/600 kcal spread out over the day, and who feel ready for skipping it all until the evening. Just try it!

I’ve only just started but I’m also using my whole calorie allowance on one meal, my dinner. I am never hungry in the morning and find it easy to go through to 16:00 before my tummy starts to rumble. Then it’s only a few more hours until I eat. Diets that have made me eat breakfast seem to trigger my appetite which I’ve found counter productive.

I’ll see how it goes, if I struggle to lose weight I will switch to the 500 calories split over breakfast and dinner.

hi – I am finding the posts very interesting. I did this on Friday (before the book arrived and at that point hadn’t seen Horizon either) however, I had 500 cals over 5 small snacks/meals.
I have now received and read the the book and definitely think the point was ‘fasting’ so I decided that today was my true Day 1 and went from 5.30pm yesterday until 6.15pm today without food.
I ate 500 cals over a 1 hour period and I have to say, my meal certainly stirred grumblings which I didn’t experienced through the day! Like Puny, I am better off having my 500 in the evening as I always find that I feel hungry mid morning after breakfast.
It’s only day one so we shall see but I have to say it wasn’t that bad. I hope to do every Mon, Wed, Fri. I have a 9lb goal (in 9 weeks) in mind and then hope to do 5:2 from there though at the moment daren’t even think that far ahead and just want to get day 2 (Friday) in the bag.

Great thread, want to come back to this.

I’m following the breakfast,no calories till dinner, 12 hours later pattern.Two boiled eggs,coffee with skim milk for breakfast. Eaten at work just before i start to maintain 12 hour break.I drink Pepsi Max during my lunch hour as i finds that makes me feel full. Sipping it while i distract myself with some puzzles.Dinner is eaten not less than 12 hours after breakfast.100g chicken with spice or fish,steamed vegetables and diet pudding or piece of fruit for something sweet if needed.Special treat is low calorie gravy.Always keeping to the 500 calorie limit. Health benefits are very important to me as I’m not ageing well but I’m focusing on weight loss with maintaining the 12 hour gap for the health benefits.So I’m fasting on consecutive days as my analyser scales/keto stix show a reduction in body fat.Not much kilos lost than a regular but no loss of lean tissue and i can still have a piece of cake if i feel like it. Certainly so much easier to do and to stick too. May experiment later with non consecutive days but want to drop max kgs for now.