Calorie limit on fast days

This topic contains 16 replies, has 11 voices, and was last updated by  TracyJ 10 years, 9 months ago.

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  • Hi, I’ve seen the doco and bought the book. I’ve already had success with getting my weight down using the Weight Watchers formula previously, but eating as much as I like 5-6 days a week certainly appeals! 🙂 (plus the additional health benefits of fasting that have been discussed) Gonna get my Doctor to do some checks before I start.

    (for men) 600 calories and “a quarter of normal calories” are used interchangably through the book. That suggests 2400 calories/10000kJ on a normal day. I already know I sepcifically have approximately 12000kJ a day without gaining weight, so does that suggest I could have 700 cal on my fast day? Since these 2 terms are used interchangably, I’m not sure whether these studies (if any) came to a calorie amount conclusion or a percentage of normal amount conclusion? Thoughts? With a curious approach, I’m looking at using the Weight Watchers formula, same as I normally would, but just restricting the points to a quarter of normal on fast days (but 600 cal would be somewhat less than a quarter of my normal)

    Also, as alluded to in my previous paragraph, what studies have been done on the amount on fast days? Just wondering where the figures came from, and if you can have more (30% say) and still get the heallth benefits? I qualify this next statement by saying I haven’t quite finished reading all of the book yet, however I’ve not seen any discussion of how this 600/25% figure was arrived at. There’s been discussion that you don’t have to completely abstain on fast days, yet not sure where the actual figures used came from. i.e. how much do you need to abstain by in order to start getting the health benefits?

    BTW I have always been someone who could eat as much as they needed and still want to eat more. i.e. never got the “full” signal from my stomach (wasn’t an issue til my late 20’s!). Was only when I saw a doco that this is just the way that some people are that I realised I would just have to put up with feeling hungry in order to lose weight (and then I succeeded). Would be good to only be hungry 1 day a week though, hence looking at this diet, and then as little hunger as possible on fast days. 🙂

    Tnanks.

    Apologies if this wasn’t the best place to post this (which I’m now thinking is the case). I came in thinking of how to approach it from a Weight Watchers points perspective, so thought this was a good place from that point of view. Now I’m thinking it would’ve been better placed (given my questions) in the “science” section. Anyways, looking forward to some feedback (even if I have posted this in not the best place). 🙂

    Don’t get hung up on calorie counting for fast days. Eat extremely little (or nothing) and don’t think about it. Eat normally/sensibly on the other days (it is not like dieting)

    Totally agree leevee, forget the calories – total fast on fast days and normal on other days. the whole idea of this “diet” is that it fits into your lifestyle – a bit of deprivation (which is easy) and then normal. It works! 14k in 20 weeks.

    Bear in mind I am not doing this diet for weight-loss, just the other health benefits (notably IGF1 reduction), so there is no point to unnecessarily depriving myself of food on a fast day, especially since I have trouble sleeping if I am hungry at bedtime (so a total fast is out). I posted elsewhere that I ended up doing a 20-hour fast my first time (skipped breakfast and lunch, then had dinner/desert), and I figure I have more than likely already gained the health benefits by then, and shouldn’t really need to cut-back on those night meals (even at 700 cal I’m having to cut-back a bit on what I would normally eat then). Unfortunately my Doctor tells me IGF1 tests aren’t allowed without a clinical reason for referral, so there is no way for me to find out myself through trial-and-error if I am getting the desired effect. 🙁 I’m reliant on research, so I’d still like to know how much I can get away with eating on a fast day, especially if I’ve already fasted for 20 hours by the time I eat for the first time (logically, there shouldn’t really be any reason to limit intake at that point – surely the health-benefit effect has kicked in after 20 hours – but this is what studies are for).

    I’m working my way up to a 24 hour fast and am then planning on having a regular dinner. I don’t have to lose weight either and I also think that it’s the fasting itself that’s the most important thing.
    The 5:2, or 6:1 that I do, gives you a great way of adding fasting to your lifestyle but it’s the fasting that counts. Not the 25% calories you eat, these just make it easier when you start.

    The 25% Calorie limit was essentially plucked from air and tested, and it worked under the conditions tested–the patients were allowed to eat all their food between 12 Noon and 2 PM, then nothing else until morning.

    At least some of the benefits derive from the cumulative weekly energy restriction. If you reduce by hundreds of Calories on 2 days a week, and don’t eat them back on the feeding days, you will lose weight and your serum markers of cardiovascular risk will improve. The question is, how precisely to you have to adhere to the original research protocols to get the metabolic benefits? No one knows. Do what works for you. If you are achieving your goals with a more liberal energy allowance, good. If not, rein it in.

    Thanks for that info. The problem is not knowing if I’m achieving my goals, as per not being able to get an IGF1 test. Hopefully there’ll be some more studies to establish these numbers more definitely.

    I started on the 5:2 plan (refuse to say diet – hate people who talk about their diets) the day after I read an article about it in the NYT in March ’13. Felt like it was magic. Down 10% of my weight in 4 months without pain. But I just read the book and found it both unnecessary (I was succeeding fine before I read it) and full of oddities. Donald, the authors never do address the obvious point that 500/600 calories is only a quarter of a minority of peoples’ daily requirement. I understand they are trying to make it simple, but again and again they repeat that you are eating a quarter of your daily caloric need. I try to keep my intake to about 400 calories on fast days, which is still over 1/4 of my daily need – about 1200 to 1300 calories (yes, I am a very small person with a light activity level). I would have felt better about the “rules” had the authors just admitted that the numbers are semi-random. The calorie counter in the book is ridiculous – what was the point of pretending a serving size is 100 g or 100 ml for every food? I guarantee that no one eats 100ml of butter for one serving (739 calories!) or for that matter, 100 ml of Coke (a mere 43 calories). The authors say they want to hear from people, so I hope they will read this and respond! And in spite of my gripes, I’m thrilled to have learned a way of taking care of my body that I believe I can maintain for life.

    I thought that too when I was reading over the calories, but I think it’s supposed to be an easy amount(100) from which to calculate the calories of the amount you’re eating. Say you have a 1000ml bottle of Coke, you could just multiply the 43cal. x 10=430. Or you could look at the bottle. 🙂 It is handier for things like fruit and vegetables that don’t come with a label.

    I agree, Christine, that that was their intent. It would be fine had they chosen more appropriate column headings than “serving size” and “calories per serving”. Well, hopefully people reading the book know that their bottle of Coke doesn’t contain only 43 calories (but I’m not sure – people can be pretty dense about these things…).

    Not sure where you are, but in Australia the nutrition information panels have information for both “per serve” and “per 100g”, though admittedly some have been lazy and said that a serve is 100g. e.g. a 500g tray of 8 sausages, which says a serve is 100g. So… you’re supposed to serve each person 1.6 sausages?? Good luck with carving up that dinner! 😉

    Why would you drink coke on a fast day?

    I think 700 kcal would be fine for you donald. The 600/500 thing is just a simple guideline, not a rule. In the US it seems surprisingly sexist, but it works for many when they start. I’ve been doing this for quite a while and I’m more like levee and just eat very little on fast days, mostly veggies and a bit of chicken or fish for protein. But it does seem to me that if you are very big or small (or high or low activity level) then the simple formula could be trouble. Dr. Mosley says you should eat some protein because your body can’t store protein and you don’t want to lose muscle. Otherwise it should really just be fiber just to fill you up with as little fat and carbs as possible (veggies). Zero carbs would be ideal, especially for insulin sensitivity, since you want to deplete the liver of glycogen.

    I guess the previous post was about diet coke. I was wondering whether, when I drink tea, does the lactose sugar in milk on fast days cause significant insulin spikes? I’ve read that the body can’t burn fat when there is insulin in the system but I drink tea half hourly!

    Perhaps.unsweetened or even sweetened almond milk may be the answer for your tea if you like almonds? The brand I use has 24 calories per 100 ml sweetened and 14 calories unsweetened, compared to around 56 for most milk.
    If you really can’t bear the almond milk, lactofree milk has around 20% less calories than standard semi skimmed.

    donald – I’m not sure where you are but you were referencing kilojoules ‘Kj’ on your initial post. The standard reference for the fast diet ‘rules’ and in the books internationally I believe, are Kcals. The 2 are different measurements of calorie content and are not interchangeable, so do be careful to take in 600 or 700 or whatever you decide Kcal rather than Kj.

    Other than that, if you really want to do the science bit then go to the ‘how’ tab and calculate your individual numbers. It will give you a TDEE (the total calories you should take in on any normal day in order to maintain your current weight (your fastday amount is a quarter of that). It will also give you a BMR which is your minimum normal intake which you should never dip below on a non-fastday.

    As you are not doing this for weight loss I’d take your TDEE times it by 7 to get your weekly calories for maintenance. Then I’d knock whatever your 2 fastday calories come to. Then I’d divide that number by 5 and use that as your personal TDEE. Then you would not gain or lose as long as you always remain roughly around that daily figure on your non fastdays.

    Additionally – to get the optimum health benefits from the actual fasts I’d make sure that you go at least 14-16 hours between beginning your fastday and having any calorie intake whatsoever. It’s the genuine (absolutely no calorie intake whasoever) fasting period that does the IGF-1 ‘magic’ and provides the other health benefits. Say your last meal is 7p.m. the day before your ‘fastday’ – you shouldn’t eat or take in any calorific drinks before 9a.m. on your fastday at the absolute earliest (to be safe I’d say give it a good 16 hours – 11a.m. – to be sure).

    Good luck with whatever you decide to do.

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