Running & Fasting

This topic contains 30 replies, has 17 voices, and was last updated by  Tennismom 7 years, 12 months ago.

Viewing 32 posts - 1 through 32 (of 32 total)

  • Hi All
    This question may have been asked before, and I apologise if it has.

    By way of background, I am 48, live in Dunedin, NZ and have been doing 5:2 since late last year. I’ve lost 5 kilos thus far and would like to lose another 3. I fast (usually) on a Monday and Friday but this does change depending on what life throws at me. On non-fast days I count calories with MyFitnessPal and try to eat around 1350 cals.

    I am a runner. I used to avoid going running on fasting days but I like to run as often as I can. Today I ran over 8km in my lunch break and by 2.30pm I had the shakes. I ended up having a small scone to get me through to dinner which will be around 500 cals.

    Is it OK to go over the 500 calorie limit a wee bit if you do a hard work out on fasting days or should I avoid running on fasting days so that I can stick to the limit?


    Susan, you probably get some people telling you that you have to stay under your 500 cal, but I believe it isfully O.K. to go over ever so slightly.

    I am very similar to you: I am 48 and I have started at the beginning of November 2013 with 65kg @ 5’7. My goal weight is 56kg of which I am just 900g shy.

    I have adapted the 5:2 fast diet completely to my personal needs also because I am getting easily bored. Some weeks I am doing 5:2 “by the book”; then I might do 4:3 or ADF depending on how I feel. Then I might be doing a week off pure calorie watching.

    All off it worked for me. I have lost over 8 kg so far, which is quite surprising as I did not have to lose too much to begin with!

    One thing though that helped me tremendously is that I have cleaned up my diet completely, cutting out junk food left right and center. No more Coke, no more coffee with sugar, no more white pasta or white rice, no more pizzas, hardly ever ice cream!
    Whole milk has been replaced with unsweetened almond milk and much more. (Well…occassionally there are some exceptions…)

    At the end of the day we all have to see what works best for us. If working out on your fast days makes you feel good then why not, even if you have to eat a little bit of something before or after your work out. If you stop losing weight then you can revisit your decision. It is at the end of the day not a race!

    You will probably still net out under 500 cal. If MyFitnessPal gifts you as certain amount of calories for your work out then I would not eat all of them back but certainly a couple.

    Best of luck

    Hi Stef
    Thanks for your reply.
    Gosh – I am 5′ 8″ and my goal is 65kg so you must be very slim! 🙂
    I feel as though, as long as I give my body a break from digesting food, I am doing something right – the fact that I have been able to come off the acid reflux meds I was on for years since starting 5:2 is testament to the fact that it’s doing good things for me.
    I think I have a pretty healthy diet – takeaways are a rarity but I do enjoy the odd ice cream. No caffeine (as it causes relux), low fat, lots of fruit and veggies. And, of course, lots of running.
    I might try planning my rest days to coincide with my fast days for a bit so that I can successfully stay under 500 cals.
    Thanks again and good luck with the final 900g! Oh – and I try not to eat all the calories that MFP gives me on my non fast days but some times I do slip up.


    Sounds that you are doing everything right. Yes perhaps coordinating rest days with fast days might be a good idea. Best of luck and keep us posted.

    Hi Susan – recognise your post is a few months old now so you might not see this but I am a runner and have been on the 5-2 for a couple of years losing 28lbs – I initially ran on fast days but now treat my fast days as rest days and run the other 5 days a week – i think you should always take on carbs before and after you run – it help prevent injury and muscle strain and keeps your energy levels at a healthy level.

    Hi Susan, I’m a runner too and sometimes run on a fast day but i usually run a little less distance than usual as sometimes i start to feel a bit weak.( I see you’re from Dunedin as well – how about that for a coincidence!)I agree with Stef. You can adapt the 5:2 diet to suit your own personal needs – if u feel u need some extra carbs after running then u should have them – no point in fainting after exercise lol!

    Thanks for your replies Jon and Patsy. I actually gave up fasting a while back as I couldn’t stick to it and constant failures were messing with my head. I am aiming to get back to one fast per week soon (on a non running day). Cheers! Susan
    (And yes Patsy – it is a SMALL world indeed!)

    Hi Susan, u sound like a more serious runner than i am. Do u run around Ross Creek? That’s my favourite route starting at John McGlashan through to the reservoir, round the hilly way round once then down into the valley ending up in Malvern St then up the Bullock Track which is really hard work – only 5 and a half kms i guess but that’s my sort of distance.
    Good luck with everything.


    I remember having just 1 instance of ‘the shakes/ uncontrolable hunger’ after a workout (2.5K in the pool for me) very early in the 5:2 lifestyle. I’d made the mistake of eating BEFORE I exercised rather than the other way around.

    Since then I have always fasted (completely) all day until my swim (and/or pilates or Yoga session) on both fastdays and as often as possible on non-fastdays too.

    After my swim I usually have a whey protein powder shake (about 70kcal) for muscle recovery and when I get home (usually after 7-8pm) I have either my full 500-600kcal fastday allowance (I’ve never been particularly draconian about sticking rigidly to 500 as a maximum and I know and accept that that may mean slower weight loss but I’d rather be comfortable with this WOE than strict and miserable) or my 1500-1800 non-fastday allowance.

    I don’t know if that’s the way to approach a heavy workout for everyone but it works for me.

    I always try to run on my fast days. It somehow feels like fasting x10.

    I usually eat nothing all day (apart from milk in tea and coffee) and run 3-5 miles at about 5pm and then only eat at 6 or 7pm. Usually use 600-700 calories (according to RunKeeper) and sometimes eat only 600 so in negative territory for the day. Hurrah! But often eat more to have net consumption of about 500 calories. My energy levels can feel low after about 20 mins running, and of course I am always aware that I should stop and walk if they go too low. But I have never had a problem for last 2 years.

    Having said that I may be used to it to some extent as I have for 20 years done a very low calorie diet for 3 weeks (rotation diet) once a year combined with cycling. It often felt like I would hit the marathon runners ‘wall’ after 10 mins cycling (of a 50 min ride). But it just meant I went slower for a time and often got a second wind.

    Hi all, I’ve just started the 5:2 & so far have kept fast days for my non-running days, although I’ve found lower impact session such as x-trainer to be ok. Might experiment a bit more once I’m into it. Good to see a variety of experiences on here, as others have said I think it’s sensible to tailor the fasting & exercise combi to individual tolerances

    I cant fast…why you are fasting?
    losing weight!
    without fasting its can be possible…..

    I’ve been running a slow 2.5 miles and doing yoga (90 minutes) on fast days no problem. My struggle entails matching low-mileage or rest days with other “good” fast days (i.e. I don’t want to fast on days with social engagements, etc). It seems like too much to juggle.

    I’d love to run a quick 8 miles tomorrow and also fast, but it seems like an ill-advised idea. Does anyone have outside limits on how much to exercise on a fast day?

    I’ve found this thread really helpful! I started 5:2 not so long ago, and have decide to try my first run whilst on a fast day.
    See how I get on later.

    Hi All.
    Thanks for all the input and advice. It’s been a few months now and I am still struggling to get back to 5:2. I just get so darned hungry on fasting days, especially when I run, that I often fail. I have regained some weight so am recommitted to getting about 7kg off and getting back to goal.
    I’ve just been diagnosed with exercise induced asthma so getting on top of that is a focus now as is reaching my running goal of 1300km for the year of 2014. I’ve got 89 kms to go….
    PS: Patsykona- yes, I go around Ross Creek and all over Flagstaff and Swampy Summit (not all at once though!!) once a week with friends. The rest of the time I run around the Uni, to Normanby and around the Highgate / Wakari area.

    its great reading your posts, i am that close to ditching this diet tbh, i am active and train (whether that be crossfit,running,spinning,weights,insanity) for about 2 hrs a day and i cannot eat less than 800 calories on my fast days and continue my training.I do not eat from 9pm -midday apart from green tea. Ive been advised on other forums to just reduce or not exercise on my fast days but tbh dont want to do that as i enjoy it so much. On a normal day I eat about 1200/1300 calories with one day which is usually a saturday a bit more… I use myfitnesspal which keeps me on track but have a feeling this diet is just not for me. I eat very clean and healthy anyway and only really want to lose about 5kg… hope you dont think im being stupid but need advice.

    Hi gini and welcome:

    You do not give enough information for help.

    What is your eating pattern? You just say you do not eat from 9pm to mid day.

    What is your TDEE?

    Here are some general tips – number five deals with the impact of exercise on a diet.

    Good Luck!

    Hi gini:

    I note the link did not post for some reason – probably operator error. Here are the tips:

    Good Luck!

    I generally eat x4 a day as that works better for me my main meal is before i train and i have a snack after training. My TDEE is 2544 . I eat clean lots protein,vegetables. Cant eat pasta or rice so use konjac and only eat gluten free wholemeal bread.
    I only drink alcohol on saturdays and thats is red wine or gin.
    I eat only organic yoghurts or muesli for breakfast. I use almond unsweetened milk and for hot drinks only green tea.
    Let me know if you need any more info 🙂

    Hi gini:

    I did not explain myself enough. By eating pattern, I meant how are you doing your two diet days each week? Are you doing the basic 5:2 (see the link I gave to see what that is), or some variation?

    Also, about how much do you weigh?

    I weigh 65kg, only want to lose 5kg tbh .
    ive been doing my diet days back to back on tuesdays and wednesdays.
    I am eating normally which for me tbh is about 1300 calories daily maybe a bit more on a saturday but not over my TDEE and i try and fast and that is literally TRY my best for two days a week but not the 500 calories as i literally cannot sustain my training/running which is highly important to me (although poorly today so only managed a run today lol) so am trying to not go over 800 calories.But everyone says no no no it has to be 500..arghhhh!!! I log everything at least 5 x a week on my fitness pal its open to view so you can use link.

    Hi gini:

    Well, taking your numbers, you should be losing about 2.4 pounds a week! As you are not, there must be something wrong with your numbers. The ‘numbers’ are never precise, but they don’t miss by that much.

    Your TDEE says you burn about 17800 cal. per week. Your 800 on each of two diet days, and an average of 1300 per day for four days and 2500 for Sat., indicates you are only consuming 9300 per week. That leaves an 8500 weekly deficit, or about 2.4 pounds worth.

    Are you sure your numbers are accurate? It is hard to believe you can be living with such a large cal. deficit and not losing any weight! Clearly, if the diet is creating that large of a deficit, it is not the fault of the diet.

    There are several things I would look at, in no particular order.

    One, most people overestimate the amount of their exercise. I always suggest that a person estimate their activity level and use the next lower level when getting the estimate their TDEE. TDEE is an estimate, after all, and it appears yours is a bit off for whatever reason. To explain further, if your calorie intake numbers are accurate and you are not losing weight, that would imply your TDEE is actually just a little over 1300! Two, if you are using activity monitors of any kind (wearable, on exercise equipment, etc.), research shows activity monitors are not very accurate – tests show that the most accurate ones are 10% off, and many are more than 20% off. Three, as number 5 in my post explains, exercise can hinder weight loss. Four, insure you are counting every calorie you ingest. Many people forget the ‘small’ amounts of food they eat/drink, underestimate portion sizes and miss big on calories in alcohol.

    I would guess that what is going on is a combination of the above – for what ever reason, your TDEE is lower than you report, your caloric intake is higher than you report, and your exercise is limiting your weight loss. The numbers you report cannot be accurate without you losing any weight.

    Good Luck!

    Have to admit not updated my weight since before xmas and i do a fair bit of strength training too. i understand re the TDEE although i dont fall into the lower catagory which is only working out 3/4 x a week for up to and hour as i train x 6 a week for 2 hrs each session generally totalling 12 hours a week. My main issue was that i couldnt cope on the 500 calories on fast days. i do also however weigh everything prior to eating/logging and as im a saddo dont buy anything to snack on,i would say the only ‘extra’ a week would be my treats on a saturday which are a bottle of red wine, a large packet of crisps and maybe a pizza (aldi), which as i have a large calorie deficit dont worry about too much. but thankyou for you advice and i will analyse things a little closer. 🙂

    My 2c on this topic. I have posted on the Type 1 Diabetes thread and this would be the main other one. I have been a well-controlled and otherwise healthy Type 1 since 1990. I started the 5:2 diet three years ago and two years ago to generally be more healthy, but as a side-effect I lost 7 kg and two years ago started running to replace my intense 40 minute bike rides up the local hill. I am now addicted to runners high and cycle only for errands. I have settled into a routine where I do not run on a Second consecutive fasting day because my glycogen reserves are lower. Running within a few hours after breakfast (my Fasting Day meal), or before breakfast during the summer, is the same as running on a non-fasting day. Also I do not run before breakfast on the first Eating Day, because my metabolism is still in fasting mode. Just in case any insulin-dependent runners are watching…I have noticed that if I run before breakfast, my blood sugar is always higher after the run (running adrenalin), but if I have any insulin depot, my blood sugar is always lower. If I run after breakfast-and-insulin, I always drink sugar-enhanced juice during the run.


    Hi, although I’m not a runner I think my sport compares-ish….I’m a curler, yup that weird sport w/ big stones and brooms on ice. You can burn up to 200 in 140 min. game.
    Anyway, I was told that if I curl on a fast day, it will negatively effect my muscles. Do you agree w/ that? They said that I should eat on a curling day so my body has fuel and calories to burn instead of breaking down my muscles.
    Just curious if this is something you agree with.

    Hi everyone,

    I’m not sure this thread is still active but I’m also a runner. I run 3 or 4x a week and cycle another day. In total I do around 5 hours a week of hard cardio, and more if I have enough time for it. My weight also decided to stay with me lately. I had to stop exercising for a couple of months and got excess weight immediately, and now it won’t go away no matter how much I run. This is my second fasting day and it has been real easy so far. My running hasn’t suffered at all – in fact I feel I’m running faster.
    I’m not running very long distances at the moment (only up to 18km) but I will start preparing for a marathon (it will be my second one, after 3 years) so let’s see how the long runs go. It would be nice to keep in touch with other runners.

    Hi FastRunner! I love to exercise too. Lately, I’ve been doing a lot of HIIT workouts on the threadmill and lifting weights. Although I’ve become more toned, I still cannot drop any weight without some form of dieting, I don’t have much to lose, but I really believe losing 5-10 pounds will help my running.

    I’ve run a few half marathons, but haven’t planned on doing a full. That’s quite an accomplishment, congrats! I do have a race coming up (only a 10k) and want to have a PR.

    I’ve been doing 5:2 off and on the past few years. I know it’s the only thing that works for me, but I usually get derailed after a few months. I have found that it negatively effects my exercise the day after a fast sometimes. Have you found a good schedule with fasting and exercise? I’m still trying to figure out the timing… Good luck with your training!

    Hi Tennismom,
    I ended up switching my fast days to Mondays and Wednesdays to avoid fasting on a curling day. It can be tough since my fast days are only a day apart but it seems to jumpstart me into better choices throughout the week. Notice I didn’t mention the weekend 🙂 Combining my fast days with rest days is helping and I have more energy on my hard workout days. I agree, I have less energy to workout hard the day after a fast day.

    I’m not a runner but a cyclist. I’m almost 3 months into the 5:2 diet and started doing some training on fast days, including high intensity intervals. I am also a type 2 diabetic on metformin. During my rides (indoor turbo trainer or outdoors) I am 67 y/o and 3 years ago had quadruple heart bypass surgery. I always wear a heart monitor and can analyze my heart rate,speed, distance and time.

    Personally, for rides up to 45 minutes I noticed no difference between my performance on fasting vs non-fasting days. In some ways it actually feels better. My blood sugars and heart rate behave normally – if I start with “low” blood glucose my readings go up. This is called a “liver dump” where the liver is responding to the need for glycogen by dumping more into the bloodstream.

    I would be reluctant to go much over an hour on fasting days, but other than that I feel comfortable continuing to exercise on fast days.

    Thanks Viking & Jennie for sharing! Jennie, I’m trying to do 5:2 on rest days as well. I’m planning on attending my workout class tonight, hoping the fast doesn’t affect my performance. Unfortunately, I’m pretty competitive and hate it when I can’t push through a workout. I’ve noticed that I can really struggle with performance on a low carb diet.

    Viking, my workout class would probably interest you. We wear heart rate monitors (everyone in class) and everyone’s % is displayed on a big tv in the studio. There’s a coach who gives recommendations on where your heart rate should be. It’s based on interval training. I really enjoy it, the heart rate monitor shows me I wasn’t pushing myself enough before using one.

    I’ll come back and report how the evening workout went (FD tomorrow), have a nice day!

    Hi Tennismom, Viking and Jennie,

    I only did 2 fast days so far (and already lost 2 kg… swing while you’re winning, right?). On both days I had a 600cal breakfast and then nothing but water and tea until the next breakfast.
    The “big” breakfast was enough to keep it going the whole day including the exercise. The only issue I had was sleeping, or to be more exact the lack thereof – I woke up after 5 hours of sleep when usually I sleep 7 to 8 hours. I wasn’t hungry – on the contrary, I felt too much energy. In the end I was able to keep myself in bed for another 2 hours, but waking up every 20 minutes. I hope this goes away but if it doesn’t it’s not a big problem either – I’ll just adapt my sleep cycles.

    Cheers, and good workouts. I will be running intervals (fartlek) tomorrow, and then it’s another fast day with a spinning class and some weights in between.

    Whoa, 2kg is a lot FastRunner, well done! I’m thinking I’ll probably average about 1 lb. (sorry, American;) a week. The scale has been hard to budge lately.

    I’m on my second fast day of the week. I’m happy to report I had a good workout last night. I had a tough treadmill workout with a lot of ab work. I’m taking off today, and expect to do some speed work tomorrow. I also need to get in a 6-7 miler outdoors this weekend.

    I’m a little worried about the workout tomorrow after a 2nd fast day, but hopefully it won’t be so bad. I could feel a little more muscle fatigue on Wed. than I normally do. However, I know I need to make losing some weight my priority even if the workouts suffer a little. It’ll be worth it if I can carry along less weight in the future…

Viewing 32 posts - 1 through 32 (of 32 total)

You must be logged in to reply.