Why WHEN you eat matters

This topic contains 139 replies, has 69 voices, and was last updated by  Jilrob 5 years, 2 months ago.

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  • Thanks Simco for sharing your experience and advice.

    Your advice in 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).

    Isn’t it possible that this could have implications for vitamin and/or mineral deficiencies (in some people at least) that might need to be addressed by either supplementation or careful diet planning on non-fast days ?

    I find it easier to fast than to control the amount of calories I eat. I intend to start alternate day fasting. Do you fast for 24hrs or 36hrs on ADF.

    Hi Happy, Peely and Blunt:

    HAPPY: 5:2 and the 24 hour fast are different, not mutually exclusive. The 24 hour fast as promoted by many goes from like 2pm to 2 pm. You eat before and after, and some eat during. Not eating on diet days while doing 5:2 actually leads to eating no calories for 30 to 36 hours – like from when you eat dinner at 7 pm on Monday until you eat breakfast at 7 am on Wednesday.

    I don’t have ‘evidence’ and I clearly stated it was my opinion. But there are several reasons for my opinion that I benefit from not eating on diet days. In no particular order of importance, they are:

    You lose weight faster because you are cutting an additional 1000/1200 calories out of your diet each week over the ‘allowed’ level of eating. It is almost like getting results you might expect to get from 4:3 without the need to do a third diet day.

    It is easier for me, because I don’t have to count calories and there is no worry about whether the food I really feel like eating will put me over my limit for the day and make me feel like a failure.

    If you believe that time between meals is beneficial, then it provides even more time between meals than 16:8 or something similar. If you think time between meals burns more fat than if you don’t have a lot of time between meals, then you burn even more fat with up to 36 hours between meals than you will with 16.

    It helps train the body to begin burning fat more quickly and you are less hungry. Most people that continue 5:2 for over a month learn after a month or so that they do not get hungry very much on their diet days like they did at the start (it ‘gets easier’). That is partially because the body is getting used to switching from using blood sugar to using fat for its energy. Requiring the body to go without a lot of blood sugar a couple of times a week helps the process along. Research and experience show that if you do longer water fasts (measured in days), after the first couple of days you are not hungry at all.

    It lowers insulin levels in the body. It is known that constantly high insulin levels in the body contribute to contracting diabetes, and that periodically reducing those levels to very low levels assists in reversing and preventing the disease. That does not necessarily happen, or happen as much, if you eat on your diet days (what you eat is a big factor, too – fat/protein, OK, carbs, not much help with insulin levels).

    I find it helps control eating on non diet days. This is more of a mental thing. By successfully going without food for up to 36 hours, you know you can go a whole day without eating. If on a non diet day you know you are going out for dinner and will probably eat a bit more than you might otherwise, you can easily skip breakfast and lunch and have dinner as your only meal, thus cutting out calories from breakfast and lunch that would otherwise have piled on the large number of dinner calories. If you think you have to eat breakfast and/or lunch to survive a day, you can’t do that and end up eating more than you really have to. I find it also helps with travel. I don’t do 5:2 when I travel, but I do often skip meals whenever possible. I have not gained weight when I travel since starting 5:2, and my willingness and ability to skip meals is major factor in that success.

    End of why I don’t eat on diet days.

    As for mice and humans, I surrender. I have no idea what mouse time equals what human time. I pick some numbers out of the air, run ratios and still do not know. There is a reason I use a 1:6 ratio, but I don’t know whether that reason has merit. I asked Dr. Longo about the relationship between mouse time and man time and the response I received was unhelpful:

    “The results you have mentioned were from animal studies and these do not always directly correlate to humans. For example, if positive results are found in mice after 2 days of fasting, this does not mean after 2 days of fasting the same results will be found in humans. After a lot of research, we have identified a few key factors in the mice that correlate with the benefits you have mentioned. From what we have seen in our studies, the positive results are not obtained from just 2-3 days of fasting.”

    So there seems to be no one on one correlation between mouse time and human time, and it appears that you need to fast longer than mice if you are a human to get the positive results shown in mouse studies. As most advocates of the 16:8 point of view support their position with studies where mice fast for 16 hours, I question whether humans will get the same benefits from 16 hour fasts (or 8 hour eating windows). Hopefully new research will help our understanding, and I certainly hope that your 30 to 1 ratio is not the number. There will be a lot of hungry humans trying to get benefits from fasting if it is (or maybe not)!

    PEELY – There is no evidence I am aware of that going without food a couple of days a week will lead to poor health resulting from a temporary reduction in vitamin intake.

    Personally, I think the evidence is that almost all people suffer from some kind of dietary vitamin/mineral shortfall even if they are not trying to lose weight. If you really want to have fun, get out your government’s recommended vitamin/mineral intake guidelines, chart your eating for a couple of days and compare. I would guess you will find you are undernourished in more than one area on a daily basis (perhaps not the same area every day).

    Given I believe that my normal diet is deficient, I have taken good vitamin/mineral supplements for a long time. I think they are even more necessary when I am restricting my food intake on any weight loss diet. Dr. Atkins required people on his diet take vitamin supplements and credited quite a bit of his patients’ improvement in health to the supplements, not the diet. I take supplements on my non diet days, but do not worry about my diet days. If I remember, I might take some Bs and C on diet days (water soluble), but I don’t take minerals as they tend to upset my empty stomach. Most doctors seem to think vitamin/mineral supplements are a waste of money, so it is up to you.

    BLUNT: The way ADF works is you go to bed, get up, eat 5/600 or fewer calories during your waking hours, go to bed, get up and eat normally – every other day. The ‘fasting’ time is generally 30 to 36 hours.

    That’s as good as I can do for now – Good Luck!

    Hi Simco,

    Your reasons for why you don’t eat on fast days seem little different from my reasons for why I eat 16:8 and no/low processed sugar/ carb. The same result by different means.

    I can’t comment on health markers because I was in the normal range anyway. But my experience is that the way I eat appears to have adapted me for fat burning. I have lost my excess and more. I am now maintaining by eating 16:8. Breakfast is the only meal I skip, and that’s daily. I eat processed carbs and sugars at the weekend, but rarely in the week (I don’t want to). I eat a serious amount of extra mature cheddar (I snack on it from the fridge when I’m hungry) and nuts. My diet is not low fat or calorie restricted (although the food groups may be restricted). If I do one ‘5:2’ day on top of this I lose 1lb in weight which, according go the maths, should not be possible.

    So you and I are different. And there are no clinical trials to date (and never will be) that have compared and contrasted the way either of us practice intermittent fasting. But we are both successful, and actually your and my real world experiences of how we have lost and now maintain weight will be far more relevant and accessible to others here than the results of scientific trials which may or may not be replicable in the real world.

    Re: supplements. Personally, I don’t see the need to supplement my diet. Now I have cut out the cheap addictive filler that is processed carbs/ sugar, the gap is filled by foods that have nutritional value. And I now trust my body to tell me what it needs (I have an apparently random urge to eat something, I assume my body needs something in that food).

    Re: of mice and men. Who knows, but I love the idea that you can reverse a mouse and make a man 🙂

    Love reading this debate. I am thinking about maintenance and why it was so easy to lose the 17 kgs in six months on simple 5:2 and eating normal fat, low carb food. No processed foodstuff. I went down 3 clothing sizes. And have stayed there. 😆

    And I ponder why it has taken more self control on non fast days over the last five months. Fast days are way easier than non fast days. I can only point to sugar. If I have sugar, I want more.

    I love my new figure. Maybe vanity and the feeling of being healthier is keeping me on the wagon. 😉 B

    Hey Happy:

    Re mice and men. Just reading a clinical study on fasting and cancer treatment. It says that one day of fasting for a mouse is equal to a one week water fast in a human: http://link.springer.com/article/10.1007%2Fs10555-014-9495-3/fulltext.html

    The poor mouse!
    Much better to let we humans do the experimentation on ourselves 😉 P

    Simco – Thanks for responding to me. I will look at government guidelines on vitamin intake recommendations.

    Hi all, I’m new to 5:2and am trying to get started. I am trying to fit the diet around my lifestyle and need advice. Firstly I am a permanent night shift worker in a semi physical job. My work hours begin between midnight and 2am finishing about 8.30am. I travel 30 mins home. Generally I get to sleep from11am till 4pm, when my children come home from school. I ferry my children to their various sports activities, dine at 7pm. Chillax with my wife till 9 or 10 pm, before napping an hour or 2 before work. On weekends I revert to normal waking hours till midnight Sunday. When are the optimum times to eat?

    Hi Albano.

    The general rule for many of us is “whatever works for you” as long as you can fast twice a week. I have done night shift (nursing) and I know it can be very hard on your bod, plus one tends to eat the wrong thing when exhausted. Just try by sticking to the 600 cals a day/night at first and experiment each fast to find the times that suit you best.

    Many of us limit it to one meal only as a decent meal can be had with the calories available. I also find once I start eating I want more and think of food constantly, like with a typical calorie deprivation diet. I just have coffee, water or even some instant miso tea to tide me over. The miso is good if you crave food as it’s very salty. Buying the book or reading the info on this web site is really useful.

    Keep trying as it is tricky at first but gets much easier. Our bodies seem to adapt more and more quickly to switching over to fat burning for energy (once stored glucose or glycogen is used up) This diet doesn’t feel like a diet to me, just a few days a week of discipline and I have easily lost 11kg since mid Sept, even with Xmas indulgences.

    Sorry I am not giving you a specific answer but just principles, you will need to experiment to see what works for you. Maybe have your main meal at the time you would have if not fasting, plus you may need to reserve a small snack for pre the drive home from work. Don’t forget to drink lots of water, really helps. And when your tum is growling with hunger, just keep busy, the feeling quickly passes! Good luck!

    Thankyou Nama, I will try!

    Dear Michael
    Regarding your recent article “Meal Frequency and Timing in Health and Disease” from your research, can you tell us what the optimum amount of time is between meals on either 5:2 diet days or normal days. Thank you in advance

    Hi Loveday:

    Dr. Krista Varady’s recent research seems to address your question. Here is her summarization of her research on the topic:

    “Quick update: Our “meal timing” study is now finished and the results have been published in the Journal, Obesity. Please find a link to the abstract below…
    Results from this study show that people can eat the fast day meal at dinner or as small meals throughout the day and lose the same amount of weight as eating the meal at lunch. This is contrary to what we expected…before the study was complete, we assumed that people would not be able to control their calories if they ate small meals throughout the day. We were wrong!
    In short, feel free to spread your fast day calories throughout the day if this works for you.”

    When you start wondering about ‘time between meals’ you are mixing apples and oranges. For weight loss, there are studies that go each way on when to eat – Varady’s seems to indicate it matters not when you eat.

    If you are talking about ‘other health benefits’, time between meals has not been shown to have any effect, positive or negative, if you are talking mere hours (16 or whatever). Positive effects are shown in clinical studies if you eat nothing at all for 72-96 hours and longer (which, by the way, equates to a mouse not eating for 16 hours, which is where the 16:8 concept started).

    It is nice to see recent research that confirms my position in number 6 of this post: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

    Good Luck!

    Hi everyone.

    Nice to read all the opinions and the debate :). my experience is this is that I from march 2013-april 2014 have been on Intermittent fasting. For me 4:3 has been perfect all the way eating one meal a day (evening) on my fasting day every mon/wed/fri (holidays free of fasting).
    In that perode of time I have lost 32kg :).. my bloodpressure went down to normal and my cholesterol is in normal range now. So overall a lot of benefits for me.
    To make it work just find the way which is working for YOU :).. 5:2/4:3/ADF/16:8.

    Good luck to all of you.:)

    Simcoeluv, you are ace 🙂

    HappyNow … I too love the idea that you could reverse a mouse and make a man but alas that is not possible. However, it is apparently quite possible to reverse a man and make a mouse. I’ve seen it happen.

    You clearly love an argument HappyNow. Please just stick to the point and let people have their opinions and eat what/when they want to !!!!

    Totally agree Famse, do what works for you. Glad to hear you have been so successful.

    You clearly love to make assumptions about, and offer unsolicited advice to, complete strangers Lyndonlodge 🙂

    And don’t worry! While I like to think I have special powers, the ability to control what and when people eat is not one of them…yet!

    Hi all,

    I am on my second day of fasting, and feeling good. my question is this, I am sticking to my 500kl on my fasting day, but I am eating breakfast, lunch and dinner. Making sure it amounts to 500kl for the day. Will this eating method make any difference in the weight loss process?

    Happy fasting 🙂

    Hi Angelpie and welcome:

    No, you will lose the same amount eating that way as any other way with the same amount of calories.

    See number 6: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

    Good Luck!

    Hi Angie
    You will lose weight spreading out your allotted calories but eventually you may find by experimenting that it is easier to lengthen the time until your first food as any food at all stimulates your appetite, making it harder to fast. Sleep on fast days is also often improved by eating the bulk if your calories in the evening. Food aids sleep.
    Check your TDEE on the homepage and calculate one quarter. 500 cals is a general rule for females to maintain health with 5:2, not necessarily your personal level. Try inserting your goal weight and ‘sedentary’ to get a more accurate idea of what you should eat (maximum) on a fast day.
    All the best, PVE

    The one reason this method appears to be in favour over other ‘diet plans’ is the simple fact it is intermittent. One does not need to suffer day after day to obtain weight loss/health benefits.
    Yes , fasting days are a small challenge as eating patterns are changed (usually in quantity and frequency) but it is only one day. Tomorrow you can have a healthy but normal meal.
    I as an obese person, understand better than anyone (non-obese) what bad eating habits do to your body and how difficult it is to back-track to healthy again. Yet to continually fail at single day fasting indicates to me that there is another issue at hand here outside of control. I would personally suggest starting a day to day journal that you leave by the fridge. Every time you go to find a snack rite one word to describe what you feel that instant. Just one word. When I started to journal my cravings I discovered my favourite words were not “hungry”, “sweets” or “bread” but “bored”, “bad tv”, “relationship issues” and so on. Emotions kicked off bad eating habits (frequency) for me and then craving took over for the portion (quantity) side of things. Like most things in life, once you catch your particular pattern of habitual eating, finding a solution may be easier. Dealing with issues at work or in a relationship can improve self esteem and reduce bad eating habits. Being truly happy does make a difference…

    Why if I have lost 16 pounds in 6 weeks has it stopped this week as I have had 3 fasting days and exercised twice at Ziumba this week not drank and stuck. To good calories intake other days why haven’t I lost this week?

    Hi clever and welcome:

    You might review my thread posted above: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

    The average weight loss on 5:2 is about one pound a week over time. Sometimes you lose more at the start, but it evens out over time. You are in the evening out phase.

    Good Luck!

    Hi Clever

    Have you measured yourself? During my weight loss last year, I found that whenever my weight slowed or paused, my shape would rearrange itself. A happy event. Over six months I lost 3 clothing sizes, so I never worried about a 1-2 week pause in weight loss.

    However, you can always kick start weight loss again, by removing processed carbs from your food intake.

    Cheers, Bay 🙂

    I’ve just happened on this thread. The topic that I am very interested in. That is When You eat matters. I think this was Michael’s original post on this topic. I have not got the time now but am going to get back to it after have done some more reading.

    Dear Michael
    Is there a link to access this article without paying a fee?
    Best regards

    I understand that as insulin rises with each meal or snack, and that the effect of insulin includes to store fat in the body, the fewer times you eat the fewer times insulin gets to work it’s black magic. This has particular potency if your are t2d. When insulin is not circulating your body is repairing and you are using your glycogen and fat stores for fuel. I gather Michael is not referring to clock time but to the eating window eg 8 hours that you may chose. That means at least 16 hours of no insulin. That is the white magic of IF or ADF.

    I also want to give another reminder of Jason Fung’s website. A calorie is not a calorie and IF is not just about restRicting cals. Have you read Michaels update book? He quotes researchers who have noticed an effect great than the sum of their parts in IF. Have a look at diet doctOr too. The fact that there is now a climate where all this great advice and support.
    Thanks for all the fabulous encouragement on all the threads I read. All the girls !!!!

    Just started reading the comments above and Michael’s document at:


    Many thanks to the kind person who uploaded it to google docs!

    I’m doing 5:2 but have been following a lot of information online about the role of gut microbiome and diet in weight loss as a way to see if I can eat healthier foods which help my gut bugs to help me lose weight.

    It all started for me with a mindblowing article I read last year about how bacteria in your gut can influence what you eat:


    This morning I came across a very interesting summary of an article in Cell about how the gut microbiome signals our circadian clocks (below is the link to a summary of the findings – see especially the diagram).


    So definitely low fat and low cal evening meals then!

    Hi everyone. I am a newbie and I plan on starting tomorrow. I am looking for health and weight improvements. Does having coffe in the morning count as eating? If my last meal of s 6 pm Sunday do I have to wait till 12pm for my coffee? I have purchased the book and will be reading up….. Thanks

    Hi Mazie and welcome:

    Coffee has 0 calories and can be enjoyed whenever you want to enjoy it.

    Also, there is no need to ‘time’ meals on 5:2. Here is some information that will answer most of your questions: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

    Good Luck!

    Mazie, black coffee or tea has no calories, but if you use milk or sugar, that’s different!
    There is some evidence that a longer fast is preferable for cell healing, but the jury is still out. However most successful fasters find it easier, once they are used to fasting, to eat nothing, just calorie free drinks, for as long as possible. Once you eat anything your appetite is stimulated, making it so much harder to fast.
    There are a lot of very successful fasters on this forum. All approach it slightly differently, but, when you find what works for you, embrace it. All the best. PVE

    Hi there, I’m only onto my 3rd week and have lost 3 kilograms (I also do regular exercise – cycling if the weather permits and gardening). While I am very overweight and should lose weight, I’ve been motivated to do this way of eating for the health benefits. As a very overweight person, I’m particularly concerned about becoming diabetic. I don’t think I could completely go without food on the so-called fast days, although I can easily manage within and even less than the 50 calories (I initially thought I was restricted to 300 calories!)I’m wondering which foods I should absolutely avoid for the maximum insulin impact? Can I eat apples, a small amount of skim milk, vegetables – is there a reliable reference anywhere?

    Hi magsta, Well done so far!

    Fasting takes a while to get used to and I don’t think many could go completely without food at first. It took me 6 months. Weight loss had slowed and I was within 5Kg of my goal, so I upped it to liquid only days to reboot. But I could not have managed it earlier, plus the weight came off steadily the first 6 months just doing straight 5:2 as the good doctor suggested.

    Re diabetes, try to choose foods with a low glycaemic index. These are foods that take longer to break down and any sugars in them are absorbed more slowly. When we eat high glycaemic index foods and the sugar is absorbed quickly, the body needs to release a lot of insulin quickly to deal with the sugar. Low GI foods tend to have more fibre and are more filling, so you are more satisfied. You can’t go wrong with non starchy veggies! And if you have time, making meals from scratch yourself will enable you to make them much healthier. Processed foods have lots of sugar and salt added sneakily usually. Mr Google will help you and there is lots of good information on this site. Good luck!

    Thanks for that Nama. I generally don’t eat processed food except for cheese, tofu and treats such as chocolate(!)I’ve just printed out a list of foods showing their GI index. While I generally make my bread with some white bakers flour to help it rise, I might have a go at making it entirely with wholemeal flour.

    Another question relates to timing, that is how often one eats on a “fast” day. While this doesn’t appear to change the weight loss, what does it do for the other health benefits?

    Hi Magsta
    When starting, it is often easier to break your allotted calories into 3 or 2 “meals” thus learning not to snack.
    Then start dropping breakfast and see how far you can push off lunch. Eg aim to do your first eating at 12.30, then convince yourself you can wait until 1pm etc 😆
    Most of us find that once we’ve eaten anything, no matter how small, our appetite is stimulated and it’s hard to ignore 🙁
    Be kind, but strict with yourself. Set a maximum calorie level. Plan what food you will eat. Spread it to suit you and stick with that quantity!
    You will find what suits you, but calorie quantity and managing that is the prority on fast days.
    Go for it 🙂 PVE

    Is eating between 12h00 and 19h00 (leaving a fasting gap of 17hours as effective as the 5:2 method? I would find the former easier.


    There is an old English saying – “Breakfast like a King, lunch like a Prince and dine like a Pauper.
    Maybe there is something in that saying !

    So is it eat as late as possible for breakfast on the fast days and then eat your biggest meal at breakfast, a medium meal at lunch and a light meal for dinner the way to go on the non-fast days?


    I take it you’ve just watched ‘Trust Me I’m a Doctor’?

    It’s interesting that the evidence is building for restricted feeding windows. I’ve long been a fan of 16:8

    Having my largest meal early won’t be a problem, but eating light…and early…in the evening would take some getting used to!

    So restricted feeding windows result in lower body fat, lower fasting blood sugar and lower fasting cholesterol.

    Reasons not fully explored, but possibly due to eating sympathetic to your circadian rhythm (don’t eat large meals later in the evening) and also a benefit of a longer fasting window.


    Hi HappyNow

    No I haven’t watched “Trust me I’m a Doctor” – was this issue discussed on this program?
    I have just read through this thread and trying to work out the best format to lose the most weight! I’m desperate to lose weight and reverse my diabetes so am willing to do whatever it takes! At the moment it seems that on the fast days the 16:8 eating format seems best – eating a 250 calorie meal at say at 1pm and one at 7pm? On the non-fast days it seems that eating a large breakfast, a medium lunch and a light supper is the most beneficial way to go and eating a low carb diet!?

    Interestingly, we found on our recent long stay in the UK, (choosing the shortest, darkest time of the year) that our eating patterns were totally different to normal.

    As we do at home, on a non fast day, we didn’t eat breakfast most days, but took up indulging in 2 small eating sessions later during the day, then a very late dinner at night. At home we eat dinner at 6.30 or 7pm, “over there” we found we wanted afternoon tea at 4pm due to the extremely early nights, then didn’t need to eat at our normal dinner time, so ended up eating very late (for me). This also meant much later nights before bed too.

    At home, we would be busy doing things in the sunlight, not eating at 4pm. Back home now, and experiencing the full force of summer, breakfast is still skipped, then a light lunch and an evening meal in the daylight at 7pm. Bed by 10pm.

    So, it seems the weather and daylight are large determining factors in when we eat. P

    I eat a bucket of chocolate every Tuesday at 15:39 and stroke my left ear with a toothpick that once visited Lourdes and I can now play the piano. Blindfolded.


    And your point is…?

    I find it easier not to eat instead of counting calories; it drives me nuts…

    Using the link Micheal gave that opens up the Abstract. Click on Full Tex Tab

    this will open up http://www.pnas.org/content/111/47/16647.full

    or you can down load it as PDF by clicking the PDF tab which will bring it up in your browser (mine is firefox) the page address is

    “…. On the other hand, a study of TRF in which healthy normal weight subjects consumed a balanced daily food intake within a 4-h or 12-h time period each day revealed no improvement….”

    Please note this is one snippet of the entire report. But it would appear that Time Restricted Fasting ie 16-8 20-4 or 12-12 doesn’t work.

    No, Simcoeluv, I think this time you have got it wrong. The “when you eat” aspect of this diet is the whole point of it. What you appear to be advocating is simple caloric restriction all the time, which has proven to be unsustainable and ineffetive.

    Hi Vero:

    I’m just reporting the results of research by one of the leading researchers in the IF field – one that Dr. M consulted and included on his BBC program. Here is one of my posts from over a year ago:

    “Dr. Krista Varady’s recent research seems to address the question of when you should eat on your diet days. Here is her summarization of her research on the topic:

    “Quick update: Our “meal timing” study is now finished and the results have been published in the Journal, Obesity. Please find a link to the abstract below…
    Results from this study show that people can eat the fast day meal at dinner or as small meals throughout the day and lose the same amount of weight as eating the meal at lunch. This is contrary to what we expected…before the study was complete, we assumed that people would not be able to control their calories if they ate small meals throughout the day. We were wrong!
    In short, feel free to spread your fast day calories throughout the day if this works for you.”

    Good Luck!

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