Running and fasting

This topic contains 21 replies, has 22 voices, and was last updated by  ayurvedic123 5 years, 9 months ago.

Viewing 23 posts - 1 through 23 (of 23 total)

  • Hello All!

    I am on Day 3/Week 2 of my fast and am feeling great. I lost 4.4lb last week and am finding it fairly easy to keep to the 500 cal.

    I am just back from a 5km run and I felt great while running. Conclusion – running and fasting can be good friends in my world!

    Now to make dinner – soup with loads of vegetables, and small amounts of noodles and chicken.

    Hope everyone is having a great evening x

    I find I can run on a fast day, BUT running the day after a fast day is difficult. I want to move, but I feel like I’m a 100 years old (even with some food in me to break my fast). Maybe it’s just me, but thought I’d comment so that if someone else is experiencing this effect they might have some insights into how to get around it.

    Yeah me too! I ran today – my fast day was yesterday – I do 2 laps of the park, the first one was fine, then the second was exhausting. I wonder why this is? Not enough carbs in the store?

    I haven’t been brave enough to run on a fast day, but it sounds like this would be fine from what you guys are saying. So I’ll give it a go next weekend – πŸ™‚

    I was dubious too, but ran 4/5 miles a couple of weeks ago on a fast day and was fine. Planning to do some lengths in the pool tomorrow am in this heat as I’ve run 10k today.

    I too was a bit hesitant to run when I started 10 weeks ago but now I find that my runs are generally stronger and faster. But watch out if my boy hasn’t got dinner ready to eat the moment I get back home!!

    Hi I’m 2 weeks into the 5:2 but would like to fast on my running days as those are the days I eat separately from the family anyway. I run with an evening running group so will not be eating my evening meal till 9pm (probably a soup) for ease, don’t think I could manage breakfast at 9am then nothing till after my run at night. Any suggestions how to work this?

    @kbabesx – ” Any suggestions how to work this?”

    I’m also a runner & run on my fasting days.

    You didn’t mention how far you run?

    Regardless of the distance, you may want to eat before you run and certainly hydrate quite a bit.

    A banana or two is a choice of foods for me.

    Let us know how this works out for you?


    Thanks rockyromero. Decided I’m going to skip breakfast and eat something pre-run instead so banana sounds like a good idea tho will need to make it into a smoothie as its the only way I can eat banana! Hopefully have better luck this next few weeks as I seem to be taking off and putting on the same few pounds so far, probably because I am starving and definitely eating more carbs than I should on non-fast days. Determined to crack this though.

    Running and fasting promote good body condition and better healthy which result to immune system boost.

    Hey Rogw, I was wondering whether you getting so exhausted was simply because your liver ran out of glycogen and you turned to fat burning? This is known as hitting the wall and can provide those symptoms I think.

    Just my two cents ^^

    I have found this post really interesting as I have been fasting for a few weeks now and have run on the same day and been fine. I ran today (fasted yesterday) and really struggled on the treadmill this morning and have been trying to figure out in my head why. Good to know I’m not the only one!

    I have done a bit of running on fast days and felt fine. So far I haven’t run the day after, instead doing weight training (like today; fasted yesterday, lifted today. Then ate some cake).

    I didn’t find any drop in my ability in the gym due to fasting yesterday. If I run after a fast day soon I’ll come back to this thread and post my findings!

    Although when I first started 5:2 (about ten months ago) I was a bit anxious about exercise on the day during a fast. When I gave it a go, it wasn’t at all bad. I actually really enjoy a run (might be 5km to 12km) on the morning after a fast day (either zero or six hundred calorie day). I delay my breakfast until after the run, but make sure I am fully hydrated before I go out. It makes brekky that much more enjoyable.

    If I ever don’t feel good about a run (it’s happened to me twice, but neither times on a fast day), then I stop and walk home.

    I’m faster on fasting days and as long as its under 2 hours I don’t really notice any down side. Above 2 hours and I really start to run out of steam.

    The only thing I would say, is if you train against zones e.g. intervals or HITs then you need to take account of your probably lower HR on fasting days.

    I need to take at least 10bpm off each zone max. I think its probably reasonable to ignore the cals burned reduction on fasting too as this is usually a factor of HR & time.

    I generally find I have a lack of go in me on the following eat day. Its the same as having a huge lunch and then expecting to train hard in the early evening.

    I started the fast diet a few days ago as an experiment to see how it works. I am training for a 10k. I tried to run after a fasting day and felt like I was dragging a brick behind me! I came on here to find out the best way to schedule my running and fasting days. I run 4x a week, so I think it’s going to be tough! I am always so hungry on the days I run that will make it difficult to fast on those days!
    I would love to hear from any other runners who also do the 5:2 fast.

    I run almost every day, and I have no problem working out on my fasting days. However, I am very slow and tired on the day after a fast. Maybe my body is too depleted by that point. I try not to schedule long runs or races on the day after a fast. If possible, I make them rest days.

    I ran 10k on a fast day and got a pb by 5min, however, I do find the day after a fast hard but unsure if this is due to eating rubbish during the day or because Im low on fuel, I work from 8.30 till 6.30 on the days I run and run after work so dont get in until about 8.30-9 pm by which point im not hungry, this week I plan to fast monday wednesday, tuesday Im running 4 x 1 mile speed and thursday I have a 10k run with the club be interesting to see how I do but Im sure its more mind over matter for me x

    Hi ,

    I run 5k’s and am finding. My times improving with the weight loss. I can and do run on fast days, Monday’s and Wednesday’s but find it harder on the 2nd fast day.

    Good luck everyone


    I am a runner on my second week of 5:2. Last week I didn’t run on fasting days; this week I’m trying it on my fasting days. When I tried interval training this weekend I bonked hard, though it’s been over a month since I’ve done sprints, I also felt a bit laggy. I just ran 4 miles at a decent clip (9:17 pace) and am eating some coaches oats + berries. Tomorrow I eat, and Wednesday, my next fasting day, I have a 5 miler planned.
    I think it takes a bit to get your body used to the different energy expenditure. I typically have taken a gel for interval training or runs over 30 minutes, which is the exact opposite of 5:2, since I was making energy readily available to my body for utilization during my runs. 5:2 should get my body used to doing a deeper fat burn, I think. Anyone else who posted here have an update on their running at 5:2 experience?

    Is there any evidence to back up the (apparent) consensus here that exercising in a fast day is fine; but exercising the day after a fast day is a struggle? I am just starting out on the 5:2 regime and am trying to work out which days to fast. Every Saturday and Sunday I cycle for 80k. On Monday mornings and Wednesday evenings I swim 1.5k followed by 5k runs. My preference – simply on social grounds – would be to fast on Fridays and Sundays, but I’m concerned that will just exhaust me. Can anyone advise me on a strategy? Thanks.

    Hey Alex. I started just before Christmas & well I’m back to square one again, but that’s ok as I lost quite a bit in that time. I’ve also joined a 5km park run every Saturday & it’s been the best thing for me. I’ve noticed my time is getting better each week & my recovery time is getting better. I’ve tried everything else, but I feel this is my thing too. Not quite running the circuit yet, but that’s the overall goal. Just joined the forum today to get some inspiration & motivation when I’m having a bad day with 500 calπŸ˜‚πŸ˜‚. Thanks!

    6 weeks into 5:2 on ketogenic diet, and have to say i can excercise after a fast day

    Perhaps becasue i have been keto adapted athlete for a good couple of years possibly(?)

    i’m good for high intensity running for at least a couple of miles. I was working on the hypothesis that as there were super low levels of insulin at this point it had enabled my fat burning to be ramped up higher than normal.

    The first time i managed 5 miles fast and appeared barely out of breath.

    I repeated this for a 10k race a week later but there must have been something i was missing as i only lasted a couple before dying a death. All i can think of was that i had eaten a lot the day before the fast day the first time

    Raced a half marathon yesterday using my old favourite protocol of carb loading and suplement with gels during race but this is playing havoc with my digestion… it appears as i have been ketogenic for so long i can no longer tolerate carbs to barely any degree. I feel nauseous & get terrible brain fog.

    i love racing and started all this to race better marathons but it appears i need to introducce carbs back in for the high intensity endurance or forget racing and continue to enjoy the stable keto way of eating… any ideas???

    loving the 5:2 diet… is it still called that if i’m ketogenic


    Intermittent Fasting is reported as a great way to get lean without going on a crazy diet or cutting your calories super low, while also building muscle.

Viewing 23 posts - 1 through 23 (of 23 total)

You must be logged in to reply.