Hours of diet: 24 hour vs 36 hour

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Hours of diet: 24 hour vs 36 hour

This topic contains 39 replies, has 23 voices, and was last updated by  dykask 7 years, 3 months ago.

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  • I began the 5:2 by dieting for 24 hours on fastdays. That is having a “normal” breakfast, then consuming only 600 cals for 24 hours – Not eating “normally” again until lunchtime the following day. This plan worked. It was easy, I lost weight and got my fasting glucose level and cholesterol down into the normal range. Then for the past two weeks I have experimented with a 36-hour fast – consuming my 600 cals in a 36-hour period – from after supper before the fastday until breakfast the second day after that (36 hours later). My experience has been that the 36 hour fast is much more difficult. I feel somewhat weak and suffer some from hunger. I am going to return to the 24 hour diet. It works, and since this is a lifestyle change not a “diet” per se, it should be easier to maintain. Please let me know if anyone out there has had similar experiences. Also, would welcome a comment from Dr Mosley.

    Hi garypatt, I too have been experimenting with different time periods recently. This has come about through different work patterns and to enable me to keep fasting twice a week I have been having a decent breakfast (poached egg, mushrooms, tomato on toast) then starting my fast. I have my 500 cal meal in the evening and then go as long as possible the next day – usually till about midday or early afternoon before breaking my fast with something like a bowl of soup. Then whatever I want for dinner that night.

    This has been surprisingly easy. I do know from what other posters say that a strict routine of set days is important to some but it’s the flexibility which has made this lifestyle sustainable for me. My weight loss has been slow but steady – just over a stone (14 lbs) since the start of this year but I’ve not got loads to lose and I’m happy with it.

    I have never done anything which has been so easy longterm.

    Good luck with continuing with what works for you best.

    Annie Somerset

    Annie –

    Thanks for the note and encouragement. I’m not into social media, but find the Fasstdiet group interesting and helpful.

    My experience has been similar to yours/others too. I lost 9 lbs first 3 weeks/6 fastdays -on 24 hour diet. 36 hour diet was much more difficult. This week I returned to the 24 hour diet. Working fine and I lost another pound.. My goal was to go from 184 lbs to 172 (almost one of your “Stones”). Mostly I wanted to get my blood sugar (fasting glucose) down and my cholesterol was way high too. Glucose level was just below diabetic. My checkup one month into the diet showed both measures well into normal range! My Doc was impressed. I cheated for one week in Sept – fishing trip with friends and family – drinking beer, eating fried fish and snacks etc etc. weight went back up to 179. After back on diet for 2-3 weeks, down to about 173 or 174. Today I reached my goal -below 172.

    I agree on being flexible. This is a long term lifestyle change for me. If I am on vacation, I am not going to beat myself up/deny the “social eating”. I also love not thinking about what I eat on regular days too. I just try to not go overboard.

    My wife is on the diet too. She has been on many different diets. The Fastdiet seems to be working for her. She has only lost about 5 lbs, but she feels better and is now wearing clothes she could not get into for quite awhile. She is not discouraged with slow progress, and I think it will be a long term solution for her too. Thanks! Doc Mosley and Mimi.

    I try not to weigh myself too often, but it seems I continue to loose a little even on regular eating days.

    Congratulations on your progress! Keep it up!

    Incidentally, I am retired US Air Force and live in Tennessee. I take it you are in the UK?

    Kindest Regards, Gary Patterson

    Hi garypatt-
    I have been doing the Fast diet for 10 weeks (and 13.8 lb lost) as of today. It has been a steady loss except for the week that I did only 24 hours as one of my fast days and I gained 0.5 lb that week. I don’t mind the 36-hour timeframe and often don’t feel hungry on my “break the fast” day until 10 am or later.

    I think everyone’s body reacts differently to this regimen. If I need to do a 24-hour fast in the future, I plan to make it a total (i.e. water only)one. But if 24-hour is working for you, you should continue. Good luck and keep going.

    Hi Gary

    Your progress sounds solid to me. I couldn’t agree more with this being a way of life. Sustaining it and living your life is the way forward. I really do think it encourages some good habits too.

    I am in the UK so we are just going into the winter weather. Given that I ate porridge on fast days all through our hottest summer this year, I don’t think I’m going to be doing things too differently!

    I also agree with Judithn that different people react differently to this plan and the key is to find out what works best for you.

    All the very best,


    Hi Gary! I was thinking about calling you Mr. Patterson but I didn’t think you’d appreciate that 😉 I want to join the Air Force in my country after college, so I have a lot of respect for what you guys do and did! Sadly fighter pilot is probably out of my reach as they practically never let women enter the program – but being a helicopter pilot sounds amazing as well.

    Anyway, enough about that. It sounds like you and your wife are both making progress and built this into your life! And I agree you shouldn’t let your social life / vacation suffer because of a diet, unless you go out with friends every day of course 😉 Being in China I quickly gave up the no-carb diet because I wasn’t able to eat out with my colleagues and stuff like that.

    I was actually doing a bit of thinking and realized that with your way of thinking (seeing the 500 calorie meals as part of the fast) I already did two 48 hour fasts. I only eat one meal a day, so I always fast for about 23/24 hours. I do feel rather hungry and weak in the fourth quarter of these 48 hour fasts, but I haven’t broken them. It’s just really tempting to start wolfing everything down I can get my hands on when I get home 😉

    Hi there,

    I know this is a bit of an old post but just wanted to find out if anyone has continued on with 24hr fasting? I am really struggling with the 2nd 36 hr fast in the week, and am trying today making the 2nd fast day of this week a 24 hr one.

    Has anyone done this and still seen good results? It just seems like it might be a lot more doable for me right now. Especially with this chilly January, makes you just want to sit down and eat a pile of hot sausage rolls.

    I haven’t done 24 hour fasting for any period of time but the odd time I have, I did not lose any weight. I am referring to a 24-hr 500 cal “fast” then normal eating. Perhaps if you could go on a true, 0 cal, 24-hr fast, you might be successful. That is really tough, too as I did it once or twice many years ago. I think having two sleeps bookending this WOE are essential for its success.
    I have lost 20 lb in 20 weeks and am fasting today. It is such a great tool.
    Give yourself a break and try 24 hour fasts for a while. It may work for you. Good Luck

    @monkeyslim – My personal way (and it is just MY way and may not suit others)is this….. I fast (i.e. zero cals) for 24 hours. I had dinner around 6pm last night and will have nothing except water and black coffee until 6pm tonight when I will have a dinner of around 300 cals and then a 100 cal snack around 8pm. I find that this suits me best. I have 400 cals total because my TDEE is 1590.

    It’s very much an individual thing. Some find it easier to have their 500 cals throughout the fast day – the things is, if it works for you then it’s the ‘right’ way.

    I don’t eat breakfast anyway and on non fast days don’t eat until around 1pm then have dinner at 6pm and some fruit around 8pm so I am actually doing 16:8 on my non fast days.

    I probably only eat around 1300 cals on my non fast days – except when someone leaves 4 chocs in a Black Magic box as happened yesterday. Well – they looked lonely and I couldn’t just leave them, could I? 😀

    I stress that this is what works for me though. You do not HAVE to fast for 36 hours if you find it difficult. Try doing 24 hours and see how it goes.

    tempting though it sounds – let someone else eat the sausage rolls 😀 😀

    Good luck x

    Thanks for the messages guys, good advice. It does seem like its just different for everyone, I guess a lot of it has to do with your lifestyle.

    @sylvestra 24hrs no food that is hardcore fasting! Im not sure I could do it, good for you that you can manage it though. I guess that is a true fast!

    Yeah its fine the 1st 36 fast day of the week, but for some reason the 2nd one is just so tough and really affects my mood/energy/sleep. so maybe Ill try this for a while and see what kind of results i get over a few weeks

    @monkeyslim – I don’t know about hardcore 😀 I’ve just reached this way of doing things because it suits my lifestyle and is working.

    When I started 5:2 I had 3 small meals per day but, not being a breakfast person, I cut it down to 2 meals. This was a breeze so I decided that I was going to do what I thought of as ‘proper fasting’ – i.e. zero calories – so went on to just one meal at the end of the 24 hours which I can do quite easily.

    Because I don’t eat breakfast and actually don’t eat till lunchtime on non fast days, I found I was inadvertently doing 16:8 on these days. This is working for me and I make sure I eat very healthy during my ‘feeding’ times.

    I try to avoid refined sugars and starches and get my carbs from fruit and veg and from natural starches. Add in walking around 5 miles a day nd it seems to be the best way for me.

    It’s the ‘do what works for you’ formula…there’s no ‘right’ or ‘wrong’ Way.

    Good luck x

    Hi everyone, I’m in my 2nd week but have started doing alternate day fasting for a try. I am averaging nearly 36 hours between normal eating. Not sure if it’s right. Finding it easier not to eat at all as it makes me hungrier. If I’m desperate I will have a Greek yoghurt to tide me over until dinner.
    I’m currently teaching my 11 yo daughter to knit so it takes my mind off the hunger.
    Cheers, Mel

    Thanks @sylvestra well I might see how far I can get through today without eating. Have only had a coffee with a milk portion this morning. So now will just drink fluids all day, I have a feeling I may crack by 7pm though lol

    @monkeyslim …if you had your last non fast day meal last night then your 500 cal meal will be this evening so it sounds like you’re doing just fine 😀 If you feel you can’t wait till then, maybe have a snack but try a drink first as that can stop what feels like hunger but is often thirst.

    keep going…it’s only for one day


    Thanks for starting this post garypatt! I have wanted to talk to others trying the 24 fast but there was some rather negative comments posted earlier that there would be no benefit of anything less than 36 hours which made me somewhat unsure if anyone else was enjoying the benefits of 24 fast I was (although 24 hours is an option in the book).
    My partner and I started the plan 3 months ago initially as 24 hour fast consuming 500 calories in that time period. We both lost weight, but at different paces. We try and aim for the longest fast stretches possible in that time. We both keep tweaking the plan to find what suits our energy levels, work demands and life style. Sometimes no food for 24 is doable, other times not. Sometimes I just accept That due to my schedule, I can only do 18 hours and then I follow up with a lower calorie day after. Whenever possible I will go for a run after my fast to really add some fat burning. Fasting for 36 hours made me feel physically weak and seriously reduced my concentration levels, plus I didn’t lose weight any faster! A fact I found surprising! (Again, everyone will be different)
    I found that the plan can make you think more about what you consume on non-fast days and make better choices – without counting calories!!! I have done calorie restriction diets before and whilst they do work, it does my head in to focus do much on calorie counting every day! It is good to see what you’re consuming in some initial calorie counts to get a good idea of how much you eat, but compared to the daily calorie counting diet, this plan is certainly much more manageable!
    We have both lost just over 2.7 kegs each and are half way to our goals weights. A friend I hadn’t seen since before Christmas remarked that she could see I had lost weight and as I left asked how I did it! It’s great to hear comments like that! (And I am happy to share the ‘secret’!)

    Those who have posted here to let others know that everyone is different and that we need to find what works best for us have in my opinion posted the best take home message of the entire forum 🙂

    Good luck all with finding your own individual plan!

    I am a little confused over this 24hr 36hr fasting.
    If I start my fast at say 6pm until 6pm the following day is that acceptable and will this diet still work for me ? I ask this because of my work commitments ,these time would be much easier for me.HELP please
    Confused !!

    The way I understand this is on fast days you eat 500 calories (it isn’t really a fast, but eating way fewer calories.) You can divide up the calories however you feel inclined to do.

    The next day is the normal calories again.

    If it is Tuesday and your fast day, eat only 500 calories. On Monday and Wednesday, eat the normal amount.

    I try to make my body go 24 hours from supper on the the non fast day to the small supper of slightly less than 500 calories on the fast day. I do have coffee with almond milk in it in the morning.


    6 PM to 6PM should be great. If you read many of the different approaches, you see that dieters find the one that works for them and their schedules. I think from reading the science stuff, that the important part is to have your body experience the fast with the concomitant system changes – metabolism, etc.

    By the way, I have been off the fast for about one month. Feel a little sluggish, and I have gained back a little over 10 lbs. My wife is not dieting systematically, but is generally eating less than before, and continues to loose weight. My excuse is we have had some life issue things going on, and we remodeled our kitchen. Stuff was all in an uproar around here. Eating out a lot is a challenge, too. Anyway, I will get back to it. Guess I need a word of encouragement. Good luck to you! Kind regards to my fellow dieters, even you other backsliders 🙂 Garypatt


    I have come to the conclusion that most of us spend our life cycling between doing what we should do and then going off track and getting back to doing what we know we should do.

    Feeling sluggish is understandable with 10 lbs gained. It is hard when the routine is broken — i.e. life is an uproar, kitchen out of order — and easier to eat out.

    You can do this. Find some way to control what you eat even if life is out of wack.

    Hi Amy! 6pm – 6pm is fine. The 24 hour fasting option is outlined in the book and also within this website FAQ section. (Although somewhat briefly which may be causing the blog confusion on this) Most people who are looking for more intensive weight loss (and who can fit it into their lives) opt for the 36 hour fast. The 24 hour is a great option for those who can’t fit it in or find the 36 too hard (eg., fatigue, dizziness, lack of concentration, etc)
    I started using the 24 hour and achieved good results. It took me a while to work out what days would be best (low activity days work best for me), when to eat and what to eat. Some combinations had me starving and fatigued until I got a good system going that didn’t hurt as much! It’s now (finally) quite easy!!! The 24 hour fast is also a great way to gradually lead up to the 36 hour fast. As You can choose when to have your 500 cals you can try and extend out your periods of fasting gradually. I now do one 24 hour and one 36 hour per week. I now can even go the entire 24 hour fast without eating – something I just couldn’t have done at the start!! Works for me, but as garypatt said, everyone is different. So experiment a bit and find what works for you 🙂
    I also stopped for a couple of weeks due to life commitments. I gained nearly a kilo, but after going back on the diet, that’s dropped off again quickly. Even staying with the fasting for one day per week is better than stopping all together ( or so I’ll try and remind myself next time!!!)
    Good luck!

    Hi all. Thanks for the good words. You are right, Summer, most of us, I think, have on again/off again periods. Took me 4 attempts to quit smoking many years ago; but I got it done, and I am now a very healthy 72 YO. I plan to start up again with my diet soon. Winter weather here has us inside for a couple of more days. I do better when I am active and physically busy. Garden is prepared. Now for some sunshine!

    I prefer the 24 hour fast, from after breakfast until noon the next day, because I really like breakfast and it makes the day go better for me to start with a good meal, and I am busy. Also I go to bed with little on my stomach that night, which helps me to sleep better. I think also food at night might more likely become fat since you are inactive. The difficult period for me is in the evening – I like to snack then, and my willpower is lower when I am tired and I am “shutting down”.

    But, I think 6 PM to 6 PM should work well for you. Since you are fasting, you probably do not snack much in the PM anyway.

    Good Luck all! Garypatt

    The only thing is that fasting is not just good for losing weight but also for allowing your system time to heal itself. So i will stick with the fasting while i can. However I might also give that tea a go!!

    I tend to have my tea around 5.30 and have a 100 cal lunch the next day with the remaining 400 at tea and then I don’t eat again till about 8.30 the next morning. This works for me at the moment.

    Hey Gary,

    I too have decided to use the 24hr fast. I have been doing it for 4wks now and I have lost 14lbs, I mainly fast Monday-Friday and still have treats at the weekend (including take outs and alcohol). I snack on almonds which seem to fill me up, my main meal is usually a salad with either meat or fish with a jacket potato with butter and cheese also salad dressing all followed by a low fat dessert. I have numerous cups of teas and coffee throughout the day and also drink a lot of water to which I do add a Vit C tablet to once daily. I feel fantastic in myself, I have dropped two dress sizes which is Great! This isn’t just a diet, it’s a lifestyle change which is so easy to do especially when I look back over the years at how many different diets I have tried and failed at and how much money I have spent on ‘dietary products’. I have a lot of negativity thrown at me, people saying that what I am doing isn’t safe or healthy but the way I see it, if I’m losing weight and feeling healthier and more active in myself then that can only be a positive thing?
    Well done with your loss :O )


    I am a new faster and was reading through this thread, I would be grateful for some advice.

    If I finish eating at around 6pm in the evening – do I fast between then and 6pm for following evening OR would I just start my fast day from 6am the following morning when I get up (which would mean I have then also had the 12 hours previous where I don’t eat)…

    Sorry – just getting slightly confused, so some straightforward clarification from someone in the know would be beneficial.

    Thanks in advance to anyone who takes the time to respond 🙂

    Hi klh and welcome:

    This answers your question(s): https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

    Good Luck!

    Hi KLH

    Assume a day is from 6 AM to 6 PM, and the night is from 6 PM to 6 AM. If you fast (5/600 calories) on a fast day from 6 AM to 6 PM – the total period you have consumed only the 5/600 calories is from 6 PM the night preceding the fast day to 6 AM the day after the fast day – a total of 36 hours. Some of us think it is sufficient to begin the fast after breakfast (assume about 8 AM) on a fast day, then consume only 5/600 calories for the next 24 hours. I have had the practice of actually continuing the fast until noon following the fast day – actually 28 hours. I do this because I think a good breakfast is healthy for me, and I need the energy. The diet worked well for me. My weight was not a real issue, but I achieved a goal of lowering my cholesterol and blood glucose level. I use past tense because I have been off the diet for a couple of months. I find it difficult to fast in the Summer when I am doing hard physical work (gardening, building things) and also exercising at the gym 3 days per week. I have not yet regained the weight I lost. That’s my rationalization, and sticking to the diet is another subject. I wish you the best in your adventure.

    Very interesting comments about 24 and 36 hour fasting. When I do a FD I just make sure I only consume 500 calories on that day. Most times I have three small meals as I can’t seem to manage long periods without sustenance. Having said that my husband and I prefer to have our evening meal by 8pm each day and we only drink water until bedtime so realistically most of my FDs are for over 36 hours. Just find it easier overall to think of it one fast day with 500 cals intake rather than something spread over 3 days.

    I did 40- 24hr fasts, and I did not lose any weight. Of those, 2 of them were actually 48 hour fasts, and 1 was a 72 hour fast. I think that I lost a bit of fat but I have gained some muscle due to resistance training, but I did not put on a lot of muscle because I’m 60 years old. I don’t eat anything during my fasting periods. During most of those fasts, I was overall very low carb. I think that always being low carb slowed down metabolism due to a drop in thyroid hormones, so since then I’ve done a few days of re-feed to carb up and reset those hormones. One benefit that I have noticed is a big change in my insulin sensitivity, and now cravings have by and large vanished, and my overall level of hunger is much less.

    Just recently I’ve changed my routine to twice a week 36 hour water fasting. I’m thinking that a regular 36 hour fasting protocol is quite a bit more powerful than 24 hour fasting, so I’m hoping that it leads to some fat loss.

    I am totally confused. I think I am doing 5:2 when my last proper meal is at 5pm, I then go without food (as it works better for me) drinking only green tea, water or coffee, until 5pm the next day and have a ‘normal’ meal. Have I been doing this all wrong?

    Depends. When you have your “normal” meal does it add up to 1/4 of your TDEE or less? If yes then no problems. If its more then youre not doing it right.

    No it probably is more. I thought a full 24 hours with 500 cals (or none in my case) was a fast day, then the next day you ate normally. So essentially I should only eat 500 cals AFTER a 24 hour fast ?? Thanks for taking the time to answer me bigbooty

    An example. You have your last meal on Sunday at 6pm and then go to bed. Then all of Monday you are allowed to have 1/4 TDEE. You can do this as one meal, 2 or 3 meals. But its only 1/4 TDEE. You then go to bed. Tuesday is a normal eating day. So essentially its a 36 hour “fast”.

    OK Now I get it. Thanks so much.

    Hi tiplet and welcome:

    This thread will answer most of your questions: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

    Good Luck!

    Thank you

    The easiest way to think about it is 1 complete day of not eating, from the time that you wake up, until you go to sleep at the end of the day. That works out to 36 hours by the time the next morning rolls around. But the fact that you ate a bit on that complete day doesn’t make a huge difference. Some people choose to not eat anything at all.

    Try either! I was losing weight with both, but with the 24 hour I was losing less. Just keep track of your fasts so that after you experiment you know if it was successful and how you did it. After several months you will be a pro!

    I’ve been having an easy time of it, and I haven’t done a lot of 36 hr fasts, but my wife is pretty much in a lot of discomfort. How long do you think it would take for her to get a lot more OK with it?

    A fasting day is 36 hrs. Of course the first few weeks are hard, but after a while there’s not much to it. Your system will get used to it.

    I do 2 days 36 hrs and it is my experience that blocking even the thought of food during 36 hrs is essential.

    Your calorie deficit should be around 1800 per day. In that way you lose 0.5 pound a day, 1 pound per week. Each pound is 1 cm from your waist. Don’t lose more than 1 pound pw.

    After having reached your goal, stay on 1 fasting day per week -36 hrs-for the rest of your life. If you go back to eating 7 days a week, you’ll be back to where you started -or worse- within the year.

    Just woke from my 2nd 36 hr fast. Feeling pretty average with a headache and had some pretty weird dreams (though can’t remember them now). Oddly feeling more “out of sorts” than hungry. Didn’t feel like this after the first one but certainly feel I want try to do this at least weekly.

    I’ve been mostly doing 36 hour fasts, although they tend to be closer to 40 hour. I try not to eat anything but sometimes will have a bowl of miso shiro, a light salty Japanese soup about 30 calories per bowl. Last fast I had to do that but I also did a harder workout while fasting to that might have been the stress that pushed me over the edge. I could have gone without it, but it is just a comfort thing. Most of the time I’m reasonably comfortable while fasting without eating.

    About 5 months ago I started by just skipping dinner and eating breakfast and working my fasts long over time. My first 30 hour fast was a little rough, but not going over 36 hours is fine. I think it is something you can get used to. I’ve been doing the 36 hour fasts for about two months and only failed once when I was sick, but went right on to fast for 66 hours after I had a meal. My body was strange.

    In general I don’t feel that consuming 1/4 of normal calories on a fast day is as good and just sticking to water and coffee. But I’m more interested in the health improvements than the weight loss. That being said the weight loss has been good and I really enjoy not having to count calories when I’m eating. However in general, when I pig out, it is much less food than it used to be. My desire to eat is strong, but I’ve gotten really used to not feeling too full.

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