Welcome to The Fast Diet › The official Fast forums › Body › Science of intermittent fasting › Why WHEN you eat matters
This topic contains 120 replies, has 58 voices, and was last updated by rosegiallo 2 weeks ago.
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21 Nov 14
We all know that what you eat makes a huge difference to your health, but what about when you eat? I’m very pleased to say that I’m a co-author on a really interesting new scientific paper “Meal Frequency and Timing in Health and Disease” published on 17th November in the Proceedings of the National Academy of Sciences, USA. It’s a review of the latest research showing the multiple benefits of intermittent fasting and also the positive impact on health of time restricted feeding (going for longer periods of time without food).
It’s a comprehensive look at the science and makes a powerful case as to why the standard approach, eating three or more meals a day, day in day out, is not the best way to go. It’s also a call to arms, urging policy makers to look at the science and put more money into this hugely important and interesting area of research.
If you have questions, do let me know and I will try to answer.
I would like to know if there is an ideal time not to eat later than on this diet.
I have heard in the past that you shouldn’t eat after 7pm.
I commute and don’t get home until 7.30 most nights. How would that effect the Fast Days? Are there optimum timings for the meals?
Timing is not important for weight loss. The important thing is how many calories you eat in a day, not when you eat them.
Here are some tips: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/
22 Nov 14
But I did hear the old phrase: Eating after 8:00 (not the chocolates!!) puts on weight!!
Although it may not be quite like that my question is if you eat really late at night, would/could this affect your blood sugar levels the next morning?
I have noticed that even if I eat something perhaps at 8 O’clock or so that the next day my glucose level can rise up to above 6!
Now I drink far more water during the day and before going to bed and have found that this has a beneficial effect on my blood sugar/ glucose levels, now constantly 5,3 to 5,5
Any ideas on this?
23 Nov 14
What a shame .. the article isn’t fully available,
Michael are the better times of day to eat than others or is that specific to an individuals circadian (or other) rhythm or is the scientific evidence simply pointing to evidence that restricting food intake to a limited time each day is beneficial.. ie not specific to a particular time of day.???
NB Am in maintenance and interested in the IF for continued health rather than weight loss now.. so when to eat is a big question I would like to understand better.. at the moment I’m eating in the evening only for 3 – 5 days a week.
24 Nov 14
If you fast from 6pm on a Sunday until 6pm on a Tuesday is that considered a 2 day fast as I find it easier not to eat anything just drink water and black tea for that time except a boiled egg and 1 slice of toast without butter on the morning of the second day fast
25 Nov 14
Tuesday can only be effectively concidered a fast day if you only consume 500 calories in total, so if you consume a lot more calories after 6 pm then no it isn’t a fast really. You can start eating normal on Wednesday for it to be a 2 day fast .
26 Nov 14
I am finding it impossible to go the whole day without eating… are there still health benefits with just 500 calories spread across the day. I get really headachy and find it really hard to concentrate and of yes CONSTIPATED. Michael or Mimi I hope you can answer about the constipation thing
Hi Lucy and welcome:
5:2 is a weight loss diet. It works because of calorie restriction. It does not matter when you eat your calories: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/
I don’t know why you continue to be such a 5:2 purist! I know you have some sort of aversion to 16:8 (pattern of eating) but the evidence appears to be building that longer fasting periods ARE beneficial. If longer fasting periods result in better fat burning, how can you say that it does not matter when you eat your calories?
You are confusing a proven weight loss diet with some kind of eating pattern that provides some kinds of hoped for benefits yet unproven. If you have any clinical studies that prove some kind of benefit from pattern eating, rather than belief or hope, I’ll be happy to read them. As of today, most studies that show IF has some benefits focus on the calorie restriction caused by IF, not benefits derived from not eating any food for a short period of time.
Most people seem to use eating windows in an attempt to eat less food – the concept that they will eat fewer calories if they only eat in a certain time period. I have seen people start with 16:8, and then go to 18:6 and then to 20:4 as they find they can easily eat lots of calories in a very short time. But if it helps them eat less, fine. Actually, the book that popularized the 16:8 eating window states that as long as you eat only in the 8 hour period, you can eat as much of anything you want and lose weight at incredible speed. I’m surprised more people don’t do it!
The general belief is that by not eating for, say, 16 hours, the body will get into ketosis and burn fat. It has been shown that ketosis is a good state for the body to be in. However, few people, if any, go into ketosis after only 16 hours. Many don’t hit that state in 24 or 48 or more hours, depending on the size of their glycogen stores. And even if they do make it in the 16 hour period, they will get out of it the second they eat food, so the length of time their body is in ketosis is measured in minutes. There is no proof I am aware of that a few minutes of ketosis is beneficial. All studies show a need to be constantly in ketosis for days on end for it to have any beneficial effect. That is why Dr. Longo’s research shows that water fasting for at least four consecutive days is necessary to derive some of the benefits that do come from ketosis/longer term fasting. As you know, Dr. M rejected that approach as undoable for the average person.
If people want to eat by the clock, they certainly are free to. But there is absolutely no evidence it will help them lose more weight faster, or provide ‘other health benefits’. And, especially for newbies, it adds a level of complexity to 5:2 that is unnecessary for it to work. Plain old 5:2 is clinically proven safe and effective as a weight loss diet and I am happy to leave it at that.
Hi Simcoe and Happy
Whether we do gain long term health advantages in a longer fasting period will only be proven by time. Just as acting on climate change now, rather than taking a wait and see approach, it is worth doing.
Anecdotally, many experienced 5:2 fasters naturally fall into the 16:8 pattern as they learn it is easier to control their hunger by delaying the first food of the day. If it is proven that it also increases the body’s capacity to heal itself, fantastic. If it simply allows you to manage your fast days better, great. Either way, your body wins.
This is totally individual and requires listening to one’s body needs, not wants. P
You do know you’re posting here on a thread titled ‘Why WHEN you eat matters’….? 🙂
As I’ve posted several times in several places, I see no harm in not eating between meals. But even Dr. M in his program attained his now famous results eating both breakfast and dinner – no time between meals issue there. However, it is clinically proven that it is unnecessary to have certain times between meals to lose weight on 5:2 (or any other diet). People have been quite successful in losing weight eating from one to several times a day on their diet days, basically because how much you eat is more important than when you eat for weight loss purposes. I am aware of people that have gained weight eating only once a day. So I stick by my advice that to lose weight on 5:2 it is unnecessary to have a certain number of hours between meals.
As for global warming, my professors told me that where I grew up – but 10,000 years ago – it was covered by over a mile of ice. All of that ice (millions of square miles of it, miles deep) melted long before humans walked the earth and started camp fires, and now the closest glacier is somewhere around the North Pole. As the earth warmed without human help, I suspect that the earth will also be able to cool down and rebuild that ice whenever it decides to – again without human help. Just my opinion.
Interesting I’m sure. But what’s your opinion on climate change? 🙂
My opinion on climate change is that the climate changes. The earth is over 4 billion years old, and it is clear that at points in the past there was virtually no ice on the planet. It is just as clear that at some points, there was a lot of ice on the planet. It appears the earth gets warmer and colder regardless of who or what is living on it. There are even scientists (of ill repute, of course) that claim the earth warms or cools depending on how hot the sun is – seems the sun also has hot and cold cycles (relatively speaking, of course). But we all know – it is indeed common knowledge – that the sun cannot possible have as much impact on earth’s weather as man can.
Just like we all knew that eating fat was bad, and eating sugar was good, for human health.
Just my opinion, of course.
27 Nov 14
Link to the full article referred to above:
It’s got a lot of information in it. Thanks to the authors.
Unfortunately it requires a subscription which I suspect few of us are prepared to pay…
It was PVE who introduced the climate change analogy, I was merely pointing out that you confused global warming with climate change in your reply. Your argument that the sun has a greater impact than anything we could do doesn’t of course mean that our actions aren’t having an effect…
To get back to the subject of this thread however, you say I am confusing a proven weight loss diet with some kind of eating pattern that provides some kind of hoped for benefits.
By ‘proven weight loss diet’ I assume you mean 5:2? I assume if it is ‘proven’ that there been rigorous scientific studies of 5:2 (as proposed in the book)? Could you point me in the direction of the specific research that compares 5:2 (as Michael does it) with other IF protocols?
On the subject of Michael’s now famous results, just because he chose to skip lunch and managed to lose weight does not mean that is the best or optimal model for weight loss. He chose it because it was a WOE that was doable for him. He has made IF accessible to the masses.
I have not had the benefit of reading the full article referred to here, but I’m sure you have, so you could perhaps enlighten us about the abstract reference to the benefits of longer fasting windows (as little as 16 hours) which result in amongst other things a metabolic shift to fat burning?
You also suggest that even if a longer fast does enable ketosis, it is a short lived state that ends the minute you eat. But what if I don’t break my fast with carbohydrate? Surely ketosis must continue?
“Unfortunately it requires a subscription which I suspect few of us are prepared to pay”…HappyNow
The article at the link I provided above did not require a subscription (when I read it yesterday and bookmarked it). And when I clicked on the link 2 minutes ago after reading your post, the full article is actually still linked, still actually free.
Nope, the linked page clearly states the item requires a subscription to PNAS….
I’ll email the author and ask for an electronic copy!
Matrika it’s telling me I need to pay for it too! Must have been free when you first downloaded/read it, bummer!
Nama and HappyNow…I just tried again, it’s fine for me. I think it must be based on where you are logging in from. I’m in Australia and the link was in a newspaper article here.
I’m sorry I can’t copy and past it, it is very long.
It is also quite technical but I would happily pay for it if I had to, it is a very good article and quite inspiring if anyone has lagging enthusiasm for keeping on.
Not possible to summarize, it is very information dense. I am a bit frustrated, I thought I was doing a good thing giving that link. I am really sorry it isn’t working for you guys.
I think it is worth going to a good library with the title and getting them to locate it for you (if you like information).
Thanks for your efforts Matrika. I am also in Aus and saw the article online today in the Sydney Morning Herald, but it still won’t let me in without subscribing. Never mind, I will find it somewhere!
Also in Australia and would have to pay. P 🙂
Abstract of article: from PNAS
Although major research efforts have focused on how specific components of foodstuffs affect health, relatively little is known about a more fundamental aspect of diet, the frequency and circadian timing of meals, and potential benefits of intermittent periods with no or very low energy intakes. The most common eating pattern in modern societies, three meals plus snacks every day, is abnormal from an evolutionary perspective. Emerging findings from studies of animal models and human subjects suggest that intermittent energy restriction periods of as little as 16 h can improve health indicators and counteract disease processes. The mechanisms involve a metabolic shift to fat metabolism and ketone production, and stimulation of adaptive cellular stress responses that prevent and repair molecular damage. As data on the optimal frequency and timing of meals crystalizes, it will be critical to develop strategies to incorporate those eating patterns into health care policy and practice, and the lifestyles of the population.
28 Nov 14
This is a free article and has the link to the paper as :-
I didn’t have to subscribe to anything to view it.
I can only get to the first link also and not the second link unless I pay. I don’t know why , maybe something to do with cookies.
I’m with micheal here.
There does seem to be an eating pattern that enables the human body to become primed for DNA repair.
With semi fasting getting near that point. But since were all different . The difference is when the focus is for fat loss or for health benefit that has nothing to do with fat loss.
The statistics are proving that long term calorie restriction is a factor in longevity. But why is that?
I would point to how the Body reacts to calorie abstainence and at which point it turns from digestion metabolism to a DNA repair metabolism. Guessing that dealing with foreign matter foods stuffs are a great priority , but when the intake stops and has metabolized the body shifts to repairing from within and does so with certain predictability.
Going out on the limb and guess is the window of eating 4.5 hours is best for DNA repair without incurring other health problems long term. There are some types of nutrition the body needs to “see” or access the DNA to determine if it needs repaired or not. So it’s a combination of nutrition and calorie abstinence that makes so elusive.
I truly wish micheal the best of luck in pursuit of meal frequency research. There seems to be more benefits for calorie abstinence of 19.5 hours to 96 hours. Than the 3-4 meals a day that coincides with the obesity epidemic.
29 Nov 14
I can’t access it anymore either, I hit the paywall too when I go to my original link now.
The $10 requested for a two day read wouldn’t do it for me, it is quite long and way more dense than I could absorb in two days or even a week, it would really take me some time to get through it following the references.
I did download it with Chrome (I thought), however it has split into a lot of small files that don’t come back together when I try to open it. I’m not computer literate enough to put it back together.
I just called my state library (NSW) and they can’t access it. I think how I previously accessed was via the article in a News Ltd paper and they had probably paid for two days access (or something).
I don’t use a printer, have a paper free set up, otherwise I drown in paper.
Not too sure if I can actually print from the two day access…does anyone know?
Happy to pay for access and go print at the library (if it allows print)…wouldn’t be pleased to pay for access and then have only two days to read a follow links to referenced articles. Don’t want a years access to all articles.
The 2 days pay for access only allows access from the same computer…
I found the article by searching for it here: https://drive.google.com/file/d/0B_f0Qx6tBS1zSmtlazdYUTRBLW8/view.
Thank you acctg,
This link worked and was very easy to down load as an adobe file. I had been trying to find a free and downloadable version. Well done!
Thankyou also from me acctg! Thank goodness some people are technically competent. Downloaded easily for me too (on tablet) and look forward to digesting it all.
30 Nov 14
I am starting the diet tonight, and looking forward to connecting with everyone.
Thanks acctg and welcome to the 5:2 family
The research is indeed interesting and ongoing. The basic premise that fasting can improve many health outcomes seems undisputed. The timing of eating appears to be important, with a lean towards at least 12, perhaps 16 hour fasts as optimal. Low carb, not low fat is also the preferred system.
All the best with your adventure….read Michael’s book. Experiment. It takes time to find what suits you, but is definitely worth it and becomes a lifelong habit.
I find over the past month that I have naturally gravitated to the 16 (or more) hour time frame. I have diner at 7pm then nothing (the evening snacks are my downfall!) until noon or even later the next day. I’ll have a 200 calorie portion and a pot of tea then around 7pm the remaining 300. This seems to be a rhythm that works well for me. Having just read the article there seems to be evidence to support this for other health benefits besides weight loss.
1 Dec 14
I didn’t do so well my first time out. I had my first meal at 3:00 PM, and probably ate enough for 2 meals. I’ll try again tomorrow :(.
2 Dec 14
I really appreciate the information. I am doing ADF for health reasons, so the research is very inspiring for me.
I am grateful that this information is being disseminated because it has occurred to me that the pharmaceutical companies are probably not going to be thrilled that so many ailments are possibly going to be avoided and healed simply by not eating.
So, thanks goodness for great science journalists and the BBC doing the work and spreading the news. I sent the article to my GP.
3 Dec 14
The paper is really interesting and brings together a large body of research in the same place. Now that the paper is available and many have had a chance to read and digest some of the information in the paper, I’m sure there are many questions. I certainly have a few.
One question I have has to do with the importance or non importance of eating breakfast.
The paper clearly questions the importance of eating breakfast. “For example, despite equivocal and even contradictory scientific evidence, breakfast is often touted as a weight-control aid (77), but recent evidence has suggested that it may not be (78).” P5
However, it also cites research that clearly indicates that for weight loss purposes, eating breakfast is the most important thing you can do to lose weight, and eating in the evening is detrimental to weight loss.
“The surprising effectiveness of TRF without altering caloric intake or source of calories suggests a potentially effective meal-timing intervention
for humans. Indeed, recent human studies suggest that earlier meal timing associates with improved effectiveness of weight-loss therapy in overweight and obese patients (24, 25).” P2
The studies showed similar results. The study footnoted as 25 was published in December, 2013, and took 93 obese or overweight women and split them into two groups. One group ate 700 cal for breakfast, 500 cal for lunch and 200 cal for dinner. The other reversed it with 200 cal for breakfast, 500 cal for lunch and 700 cal for dinner. While both groups lost weight, over 12 weeks the big breakfast group showed a weight loss 2.5 times that of the big dinner group, despite eating the identical number of calories (8.7 kg. v. 3.6 kg.)!
“In summary, our results demonstrate that high-calorie breakfast shows increased compliance and is more beneficial than high-calorie dinner for weight loss, insulin sensitivity, and hunger suppression. Our study indicates that avoidance of large meals in the evening may be particularly beneficial in improving glucose and lipid profiles and may lead to reduced risk of type 2 diabetes and cardiovascular diseases. Thus, in people affected by the metabolic syndrome, dietary recommendations aimed at weight reduction and prevention of high postprandial insulin excursions should include advice on time-of-day of nutrient intake in addition to the overall food intake. However, the long-term potential health benefits of high energy intake in the morning need to be assessed.”
This research explodes the calorie in/calorie out theory and contradicts pretty much all research to date on the subject (probably why the paper used the word ‘surprising’). TDEE as a single number no longer exists – it seems to vary depending on when you eat. I’m surprised there have not been world wide reports of the research, and tons of diet books hitting the market, all trumpeting that if you eat breakfast (and don’t eat dinner), you will lose weight!
I would be interested to know why the paper’s authors question the importance of eating breakfast?
Interesting concept but not new for russian people. I grew up in Russia and most famous saying from Russian general from 1812 is: Eat breakfast alone, share lunch with the friend and give your dinner to your enemy. I guess he was right all along. My parents used modification of it – You need to eat your breakfast (and believe me, we are talking about very large breakfast, spaghetti and meatballs for example), you never know when your next meal will come. May be that’s why we did not have obese or overweight epidemy in Soviet Union.
4 Dec 14
Two more studies finding mice do better when eating in an 8-12 hour window:
Although hard to compute accurately, an 8-12 mouse window is about a 1-2 hour human window.
Simco, similar to you stating that people should not introduce exercise too early when starting 5:2 for fear that too many life changes may undermine the long term adherence to fasting, anecdotal evidence, time and time again, on this forum, indicates that many, many fasters find delaying eating as long as possible on a fast day makes fasting much easier.
Whether you believe eating in a limited window has health benefits, or not, delaying the first food of the day makes fasting significantly more doable and, therefore, long term sustainable. PVE
How does that work Simco?
intuitively, given that one mouse year equals perhaps 30 human years, then wouldn’t 12 hours for a mouse equate to a greater not lesser amount of time for us?
You are right – an 8 to 12 hour mouse window equals, given the numbers I work with, about a 48 to 72 hour human window – which is unhelpful. So the question becomes how do you reverse it so that what works for a mouse equals human time? You have to reduce the mouse window into that of a human day, which is why the human window is smaller than the mouse window. As I say, that is hardly a precise exercise. (And using one year to 30 would require that humans eat all of their calories each day in a couple of second eating window to achieve the same results the mice enjoyed.)
PVE – The discussion does not revolve around when you should eat on a diet day. I constantly give the advice that many people find one evening meal high in fat and protein works best on a diet day.
The issue revolves around non diet days. If you believe the research cited in the Mattson/Mosley et al paper above, the best thing to do is to eat early in the day and eat little or nothing later in the day – see my post above. However, the paper suggests this would be inappropriate, which is why I asked the question.
Speaking of eating windows, the same Mattson/Mosley et al paper cites research that people eating all of their meals in a short eating window experience higher blood pressure, higher blood sugar levels and higher cholesterol levels and one even concludes that it is the calorie restriction, not the window, that makes the positive difference in results. But the paper states (without citations) that eating windows might be a good thing to incorporate into your eating pattern.
I happily go with the flow of research – knowledge in this world is changing and expanding daily. But I think the research on eating windows is unclear at this time. Until it gets more ‘confirmed’, I see no reason to make a very simple and effective diet more complicated by injecting the clock into daily eating patterns. If people want to do it, however, that is certainly up to them and if they live longer, lose weight faster or feel better doing it, etc., great! But if people ask my advice, I won’t advise that they do it – today. However, new research may have me advising it tomorrow. Or pointing out that it is just another urban myth. Research will decide!
And what has been YOUR experience with 5:2? Do you eat 3 times a day? Have you found some methods easier to adhere to? Have you had life changing health benefits from this woe? This forum is full of people sharing their own personal experiences. How have you found it? We’d love to know. PVE 🙂
5 Dec 14
I play around a lot with it for various reasons – sometimes use myself as an unscientific study (see my exercise experiment in my exercise post). I also don’t do it when I travel – by choice, not because it can’t be done. So while I started 5:2 about 20 months ago, I have actually been on it quite a bit less time than that.
Overall, when I do it, I do 5:2 only. I never count calories – on either diet or non diet days. I usually don’t eat anything on diet days because if my goal is to lose weight I figure I might as well eat less rather than eat more. And it is easier. On non diet days I eat whenever I want to (normally). Some days twice, some three times, sometimes once or twice combined with ‘throughout the evening’ with friends at a pub or party. I eat foods I want to eat – I do not restrict carbs, fats or protein – or favor any one of them. I enjoy everything from bagels to well marbled steak, whisky and beer to vegetable juice.
I have lost 40 pounds since I started. My weight loss pattern has been steadily down in the sense that I do not lose 10 pounds and then gain 5 and then lose 10, etc. I do have plateaus (as I define them in my plateau post – one month or more), always because I am eating quite a bit on my non diet days, not because the diet has stopped working.
I don’t worry about the other ‘health benefits’. The research shows weight loss is often accompanied by lower blood pressure, better cholesterol numbers and better triglyceride numbers. The research does not show that IGF levels improve (in fact, going from memory, Harvie’s research indicated they went up, and aside from Dr. M’s in the program, I’m not aware of any reports of a decline).
I’m quite happy being 40 pounds lighter, and look forward to going down some more. It is a nice change from the multi-year increases I am used to experiencing. And the fact that I can eat normally really helps in continuing with the program.
I think you know I believe 5:2 is a very good diet. That is one reason I try not to make it more complicated. It is proven safe and effective for weight loss, and if a person wants to lose weight, I believe it will work just fine if they do it right. If they want to also superimpose timed eating, not eating certain foods or making sure to eat others, or anything else, I have no problem with that. You know, whatever works for them!
But I don’t believe any of that is necessary to achieve good weight loss results with 5:2.
Hi again PVE:
I guess after all of my previous post I did not give any advice (although I realize none was really requested). But thinking about it, here is my advice to anyone finding this site and wanting to lose weight:
1. Confine your diet to the 5:2 eating pattern. Do not do 4:3, ADF, 24 hour fast, 16:8, 20:4 or any other eating pattern to lose weight.
2. Although 5/600 calories are allowed on your two diet days (or 25% of your TDEE), strive to get to a point where you are not eating any calories on your two diet days (this may take awhile).
That is my advice in a nutshell, but I realize it is not for everyone!
Thanks Simcoe for your detailed response. Your experience is a great contribution to the greater knowledge about 5:2 🙂
I agree, we are all simply unscientific experiments. Fascinating, isn’t it?
Great to see your personal of 5:2.
Re: your points 1 and 2 though, are they not mutually exclusive? How is not eating any calories on a diet day different from e.g. a 24 hour fast or a restricted feeding window (and it certainly isn’t 5:2 by the book, which you always promote religiously). What ‘evidence’ do you have for ‘2’ (and compared to other models)?
Also I’m afraid I still don’t understand your logic in reversing a mouse to make a human!
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