Any endurance / longer distance people on 5:2?

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Any endurance / longer distance people on 5:2?

This topic contains 24 replies, has 20 voices, and was last updated by  Glen999 4 years, 7 months ago.

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  • Hi, I’m an experienced endurance athlete, running marathons and long distance triathlon. Even with my level of exercise though, I have always struggled to lose weight (I eat too much!). I never seem to have the discipline to stick with reduced calorie diet for long so hence why 5:2 appeals.

    I’m currently in an easy, low mileage phase of my training, so thought this would be a good time to give 5:2 a go and I’m 2 weeks into it. So far I haven’t had any issues around training on my fasted days (or day after fasted days), but my sessions are no longer than an hour and easy. Generally I train every day.

    I am interested to hear if there’s any other longer distance runners or triathletes or other endurance athletes and your experience doing this. In my current phase I think I’ll be fine, but not sure how I’ll go when I need to step up the intensity / volume.

    I walk on the job alot everyday 8-12 hours on average. I know thats not exactly the same. I get approx 70,000step minimium per week.
    I just want to say I think fasting intermittent style and walking or running compliment eachother. I wish you luck and best wishes.

    Hi runningrunning!
    Finally someone else that despite running marathons can’t shift the weight! I have done triathlons and marathons and was convinced I am the only person to not lose an ounce in trainjng! I do eat too much though. I am on a half marathon plan at mo and am in a mileage heavy week this week so have a 7miler falling on tomorrow’s fast day… Plan is to have small brekkie, banana and black tea and then run around 6.30 pm before a fishcake for tea. Will see how I get on….
    Please stay in touch as would love to hear how you plan round longer distance training

    I do early-morning runs on Monday (track) and Wednesday (tempo-ish), which are my fast days. An egg or two satisfies me until the afternoon, when I usually have to have some trail mix to keep me going. Salad or grilled McWrap for dinner. Saturdays are long runs of 18-24 miles, but I’ve eaten normally on Thursday and Friday so I’m not on fumes. I do have to eat on these long runs though, or I conk out. I’ve been doing intermittent fasting for 7 or 8 weeks now, come from 162 lbs to 155, goal of 145. I do note that a big salty meal can swing my weight up to 4 lbs.

    I am a over weight marathon runner, well actually i am not massively overweight, i’m 158lb and want to be 125lb before my next marathon on October. Currently training for July Half. Would really love to hear how training goes and whether performance has suffered as a result

    Wow – that is some weight loss you are aiming for! How tall are you? I’ve been out of the loop for the last couple of weeks with horrid virus so no running. Back on it now though and back to proper fasting too.
    10 miler today, then fasting and a four miler tomorrow.
    How’s everyone else doing?

    I am also one of the those endurance guy with a problem keeping the weight.. As a cyclist I tend to eat too much or not enough and in the off season, going to the gym doesn’t help keeping the weight down. I am trying this 5.2 for the first time. I have tried others but it has not worked after a while, so i am really hoping this might.
    So far, the 3 fast days i have experienced have gone smoothly. However I do miss ” fuel” on the long rides during fast days. Any suggestions for that from the forum’s members who might have the same experience and have found a solution?
    Also I am still struggling with what constitute a ” fast day” is it 24 hours between normal meals or actually 36 hours from last normal dinner to first normal post fast breakfast? I really like to know that

    OP here with an update. Im in 2 minds about doing 5:2. I initially did it for about 5 or so weeks. Fast days I had no issues but found myself overeating on non fast days. Some days I was massively overeating/binging. That said, I didn’t gain any weight and did lose a little.

    A couple of weeks ago I gave up on 5:2 and went back to calorie counting again. I was starting to think that this is not sustainable / healthy for me. After a couple of weeks trying to calorie count I was still overeating and lacked discipline and my weight has gone up. So this week I’m back on 5:2 again but need to try to be a bit more disciplined on my non fast days.

    In terms of training, I’m doing fine on fast days. I train most days so it’s hard to schedule fast days on rest days. My sessions are mostly in the morning. If it’s an easy short session I’ll do it fasted but if it’s a longer session or harder I will have a gel before heading out. I try to count that in my fast calories for the day but if I end up over I don’t worry. I know that you are not supposed to eat back exercise calories but I’m adjusting the rules a little bit to have some fuel for these sessions if I need to.

    So dedelou in answer to your question about fuelling sessions I am adjusting the rules a bit and fuelling during the session. However I don’t do long runs or rides on fast days.

    dedelou in terms of fasting time 24 v 36 hours. I believe it is 36 hours. However I wonder how important it is to get to 36hrs. For example Sunday night I had a late dinner at about 8.30pm. And then I had some dessert around 9.30pm. Yesterday I fasted. Technically for today, to make it to 36 hours I would need to have breakfast 36 hours after I finished eating (9.30am). If I have breakfast at 7am, so fasting for about 33 hrs, is that enough or do I need to hang out until 9.30am?

    yeah. Thank your for your comments. So, exactly Runninggrumming. How obsessive do we have to be with the time elements? Does an hour actually makes a “real” difference or it’s all about tailoring the schedule to personal realities and constraints.
    By nature, I am not a strict follower. Like you i tend to be capable to adopt and bend the rules. I must say today on 40 miles with stronger and faster guys, I was able to sustain the efforts for 36 miles and then I did bunked. I think i could have used a gel at the 20 miles round about, but that really may defeat the purpose of forcing the body to fuel on fat reserves, doesn’t it?

    Hi All,

    I’m definitely NOT a runner but I am a distance swimmer. Prior to 5:2 my only REAL exercise was 1-2 1-hour swimming sessions at my local pool per week. In that time I would swim 2.5k (so 2.5-5k per week) and once a year I would do 5k in one go at a swimathon.

    To start with on 5:2 I would avoid doing my fastdays on the same days as my swimming sessions but after a few weeks I had to flex and do a swim on a fastday. It went horribly wrong and resulted in me having to have a slice of cheese (on top of my 500kcal allocation) after my swim, as I had stupidly eaten my 500kcal meal BEFORE I went swimming. Since that mess up I have always done my fastdays on my busiest days at work and after swimming in the evening I have had my 500kcal. That worked well for the first 18 months, during which time I lost about 4 stone.

    I then joined a gym, determined to ‘tone up’ as I closed in on my goal of 10stone SOMETHING (anything). The toning has gone well and I am much fitter now than I was this time last year. I’ve discovered Yoga, Pilates, Body Combat and BoxFit classes and done a bit of resistance & weight training as well as continuing to swim at least 6-10k most weeks (for a while there I was doing 15K a week). Unfortunately the increase in exercise has not helped me lose weight at all though, so I’m currently having a little break and concentrating more on the diet itself. I highly recommend doing any exercise on ’empty’ if you can though, I always found I was quicker and felt lighter in the pool on fastdays, even when I was knocking out 4-5k. On non-fastdays, even the smallest, healthiest lunch would weigh me down a little.

    I’m a cyclist, but I haven’t tried to ride on my fast days, which are Monday and Thursday. I don’t know that I’d be able to get through one of our typical group rides on a 600-calorie day.

    I still stick to my usual amount of exercise the other five days of the week, with rides of 55 and 75 miles on Saturday and Sunday. Last Sundays’s ride was 83 miles at an average speed of 20.3mph, and I doubt I could do that without eating.

    I might try an indoor ride on rollers just to see how far I can go without keeling over, but even that isn’t the same as having to do 30+mph sprints to catch people on a road ride.

    Hi, I’m training for my second marathon. I have always struggled with weight, although I’m eating healthy. I’m a woman, 1.72m and 66kg now. I have been on the 5:2 for 3 months now. At the beginning I was losing very slowly but then I realized that old clothes fit me again. After 2.5 months I was down 4kg. Now I had to step up my marathon training (only 18 weeks to go) and I noticed that I have gained 1.5kg! I’m not over-eating on my non-fast days and I do train on fast days (just no long runs over 10k). I fast on Monday and Wednesday but sometimes I find myself fasting into Tuesdays as well, just out of habit.
    So no idea why I’m gaining weight again?! It’s frustrating. Anyone else with that experience?
    My percentage body fat has gone down though, that’s the only good side effect.
    Not sure if I should keep on doing the diet while training more intensively.

    it might just be water weight from inflammation from increased training. If your clothes still fit and your body fat % is down, I wouldn’t worry.

    Thanks MaryAnn, I didn’t know that! That might be it! Also because temperatures are 35degrees Celsius and 80% humidity…so probably water retention on top of inflammation.

    In September, I’ll start training for my 4th marathon – hopefully at a much lower weight. I’ve been on 5:2 for 6 weeks (one 36 hour fast and one 24 hour fast per week) and have lost 10 pounds. I have 10 more to go for a goal weight of 110 pounds (I’m a 49 year old woman, 5 foot 4 inches).

    I took up distance running in my mid-forties to try to keep my weight in check, but the pounds kept creeping on. I am taking 3 months off from running to heal an ankle. In the meantime, I do an hour+ of mixed cardio on fast days and weights 2x a week on feed days.

    I’m hoping to adjust my fasting when I start running again – maybe two 24 hours fasts a week. One huge benefit of this diet is that now exercising in a fasted state is easy – actually it feels great! I used to get tired if I didn’t eat something before and sometimes during cardio workouts longer than an hour. I’m hoping I can scale back the gels during my next marathon and avoid the G.I. issues I’ve had in the past.

    Thanks for starting this thread. It’s good to hear from other people trying to work IF into their endurance training. Here is a great article with links to several studies I hadn’t seen before:

    Pleased to have found this thread, as it’s something I’m a wee bit worried about! I’m not as athletic as some of you in here, but ran a half marathon last year and loved it. I’d love to start training for another and maybe a full marathon, but I’m also really keen to try 5:2 and shift some weight (running has zero effect on my weight, I think I just eat it all back on). I’ve always been an evening runner because I just cannot cannot do it on an empty stomach. I haven’t quite worked out a plan for how to exercise around fasting, but I figure I’ll give myself a couple of weeks to get used to the diet pattern and then experiment with exercise! Would be great to keep hearing others’ experiences and tips!

    Hi Kate,
    I took up running at 52 and have completed x5 half marathons, but I am slow, not a natural runner. You cannot outrun your fork! You will get a better shape and increase muscle mass which will burn more fat, but really run because you want to get better at running rather than expecting to lose weight. During the last Half in Sept I consumed 3000 calories but actually used half that during the run, but I still didn’t actually put any weight on and I looked so much better in the race pictures than I did the year before! I can do 2 or 3 miles on a FD but generally run on a NFD. If I am doing more than that then I plan running first and then fit the FD around that. I usually stop the FD in the last 2 weeks just because I want to give myself the best chance of getting round uninjured and not last! It may be psychological but it’s what I do.

    Hi Kate,
    I just finished my second marathon. I did the fast diet when I was training lightly but stopped it 8-10 weeks before the date.
    I realized that last year when I trained for my first marathon I believed I had to eat gels and power bars etc. So I did not loose anything. This year, first with the 5:2, then with not supplementing my runs, I lost a total of 5kg. I think you can do runs for up to 2 hrs on the diet but if you need to do long distance runs I would eat normally. The body learns how to draw from its own resources again.
    I’m back on the 5:2 for maintaining the weight (still running to stay fit), and I feel that my body needs it.

    I started a sort of 4/3 in Jan, I am an OG road cyclist, but most winter riding is indoors and the protracted winter meant than I have only been riding outside for the last couple of weeks, solidly. I found that as long as I am riding for about 90 mins I am fine on a fast day (fast days are probably better as I am topped up from the day before). Indoor rides didn’t worry me at all, outdoor rides are more challenging as I live in an area with a lot of climbing, so if I am planning on a long ride I will have a banana and a mandarin before I ride. I do carry emergency calories though. I would estimate that I ride off about 4000 calories at a min most weeks.
    FD’s are usually about 800 calories in for me, as I refuse to give up my homemade lattes. I often ride post FD on minimal calories in, because I would have just eaten something later morning, maybe a couple of eggs on toast and coffee and tea. I have lost about 16 pounds in 3 months (from 145, so not super heavy in the beginning). I think as long as we understand that should we actually ever get to the point of glycogen depletion (which I have to say is unusual for most of us, assuming we probably have at least 2K of calories in stored glycogen) that we just continue at a slower pace. I am finding the FD riding outdoors is totally fine, I feel energised, the post FD rides in the morning feel more sluggish. The net gain of the net loss is that the hard uphill riding is so much easier and I am faster this year than ever (low bar LOL, but it is me vs me). I will probably do 5:2 once I hit under 125 and building up to 3/4 hour plus rides as the weather breaks. Like many cyclists I am happy to eat way too much so I think 5/2 with 800 cals in on FDs isn’t onerous. I definitely overeat on non fasting days, now I ride outside I don’t count calories at all on NFDs. I did keep calories in on NFDs in the indoor riding winter period to 2K, and 800 on fast days. Now though, I won’t worry about NFDs calories but keep an eye on weight. Hopefully the 2 days a week will work well for maintenance.

    not sure if any of you are still doing 5:2 or still on the forum
    i am a marathon/ultra runner and was pleased to see this thread
    just wondering if any of you are still doing it and how it is going with your training
    i am in down period at the moment so try 5:2 so far so good
    but when i start marathon training i think ill take my FDs up to 800/900 i dint think 500 is enough cals for hours of training at a time
    i am lifting weights more on my down time and find i can lift too heavy as get light headed on FD
    hope to hear from someone in the same boat

    i’m about to start training for a triathlon in July, and plan to use 5:2 to lose/keep weight off. I do think that running distances up to around 7 miles are quite possible for me, whilst fasting. And I think that the short term loss of not being able to do longer runs or intervals on fast day will result in longer term gains. If I’m lighter, then I’m faster on race day and I absolutely HAVE to beat my friends on the day.

    Hi Rainbowbrite, and Richard! I’m about to start half marathon training. I’ve been a shorter/medium distance runner for over 20 years (2-5 miles a few times a week regularly) with an Olympic tri mixed in; I did boot camp classes for years including through pregnancy, and have done some home weight training for the past 6-12 months.
    So far, one month in on 5:2, I’ve:
    *Run over 5 miles on fd – this is on the farther end for me.
    *Run 3-4 miles easy on FD. Yesterday 3 miles breaking 8 min/mile pace, last week 4 miles the 9 min/mi – these are fast paces for me at light perceived effort. Before 5:2, I was interval training 1-2 days/week, and I had not been able to break that pace on an easy run, so either my body is starting to figure out fat burning for fuel or the four pounds I lost in the month have translated into some increased power. Or a combination of both.
    *Done one day of weight training on FD and bonked hard later in the day. I’m going to try again this month paying closer attention to my hydration. I only tried interval training once on a NFD and it was also a bust, not sure if the fasting was affecting my overall power, though it was early on in the month.
    *My eating/nutrition on NFD has swung between binging or not eating enough; I really need to pay closer attention. I was proud of myself the other night, putting on my big girl panties the other night when I was starving – instead of going for the chips I made a spinach/kale/hummus/turkey salad and had some tea.

    This month I’m going to try to: 1. keep long/interval runs not on a fast day 2. Run 3-4 miles or lift light on FD. 3. Begin half marathon training, which I need to do by first making room for a 10k. Hopefully I can get that in this weekend 4. Be more intentional with planning my NFD eating.

    Hope this thread keeps up and we can keep encouraging each other! I hope you don’t mind me here even though I’m not as long distance/endurace experienced!

    Hey there,

    I hope any of you is still reading this 🙂 I signed up for this forum just to join your discussion, as I am really happy to have found it!
    I am female and regularly run half marathons. As some of you mentioned as well, l have problems maintaining my weight, although I run 40 – 60 km per week. I always hate it when people say “you just have to exercise and eat healthy to lose/maintain weight.” I DO eat healthy, but I just LOVE to eat 😀
    Before intermittent fasting, I always struggled to keep my weight below 60 kg (I am 165cm) and found myself getting a bit too obsessed with counting calories. So when I saw a documentation on the TV, in which a scientist talked about intermittent fasting and all the benefits for brain and heart, I was extremely interested. I am a molecular biology, so first I looked up scientific publications and was amazed by how much literature there is! Especially compared to all the other diets that do not have any scientific basis!
    I was convinced tried it out. I am now doing intermittent fasting since April and feel great!
    I do one to two fasting days per week. On fasting days I eat about 300 – 400 kcal, mainly from fruits (Yes, I can easily eat 1 kg of fruits a day 😀 ). If I happen to do sports on fasting days, I eat something small, like a banana, before and a small meal afterwards, roughly balancing the calories I’ve burned. On non-fasting days, I do not restrict myself at all (as my goal is to maintain my weight and muscles, not necessarily to lose weight). In the beginning, I counted calories to see if I end up with too many or too few calories over a week. The result: On NFDs, I eat about 3000 kcal (but also usually burn 500 – 1000 due to running) and the net balance over the week is mostly 0, sometimes with a small deficit of about 1000 kcal.
    I am not so much afraid about training in a fasted state, but more about regeneration during fasting. I usually fast Monday and Friday which are either rest days or I do only easy runs. However, when I have a competition on Sunday, I wonder whether it is detrimental for regeneration when I fast the next day? Similar with hard interval trainings on the evening before a fast day? Any experience with this? Is there anyone who is doing fasting and endurance training for a longer period of time already? Would love to hear your stories 😊


    just started doing 5:2, although i have been IF for about 6 months.

    I was low carb for a year or so prior to the last 2 years, for which i have followed a ketogenic lifestyle.

    I feel so much better with this way of eating.

    I do however race marathons, of which i have done about 30 all in all and am getting very close to breaking ‘3’! I’m also doing a few ultras and recently completed a 100km, keto stylee.

    My trouble has always been high intensity endurance on minimal carb. And then carbing up for big races makes me feel nauseous, and fuelling during races…

    Maybe i should be upping my carbs, but historically i too have found it difficult to keep the weight off, and the low carb really worked for me… i’m still about 168lb with an ideal race weight of 161lb.

    Would like to hear also of peoples experiences with regards to when to train hard/easy and how to best fuel after hard session for max increase etc..

    Have fun all


    Hi, I am starting today with the 5-2 Fasting. As its Sunday I thought this is a good relaxed day to start. I want to do a 2 hour cycle on my racing bike (as I like to do on Sundays), about 40 KM, steady state, relaxed for me. I wonder whether I should add on calories today? I should burn about 600 cals extra. Depending on how I feel I would add on 600 cals of food. Would I loose the fasting effect if I eat 1200 cals today. It seems so much more.

    I’ll go by how I feel and will add food if needed.

    Has anybody go tips for me regaring fasting days and endurance training especially cyling? Thanks for tips. Good luck with fasting.

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