Help - half marathon on keto

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pobalita
pobalita Posts: 741 Member
in Fitness and Exercise
I'm looking for some help with fueling for a trail half marathon tomorrow. I've been running halfs for a long time (at least one per month for several years) and generally fuel with about 300 - 400 high carb calories before the run and 1 Clif Shot (25 g carbs) at about the half way point.

I switched to a keto diet just after Christmas to lose some weight and control blood sugar. I have a half marathon tomorrow and I know I am not fully fat adapted. I run three miles or more most days and have no problem, but I bonked severely in an 8-mile trail run (lots of elevation) a few weeks ago.

I don't want to bonk tomorrow, so I'm looking for advice on how to fuel for this race. I don't care if I fall out of keto for a couple days - I just don't want to feel like crap during the race. Should I load carbs tonight? Should I just eat my normal breakfast and Clif Shot? Any advice appreciated.

One final note: I'm not worried about racing or pace. I'm not a competitive runner and only do it for fun so I don't need to fuel like a pro athlete. I just want to finish with a slow, easy pace.
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  • speedingticket
    speedingticket Posts: 73 Member
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    How long are you expecting to take to finish, roughly?
  • pobalita
    pobalita Posts: 741 Member
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    It's a trail run, so I'd be happy with an 11:00 - 12:00 min pace. 2:30'ish? (I'm old and slow.)
  • tcunbeliever
    tcunbeliever Posts: 8,219 Member
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    as you have stated, you are not keto adapted yet, you should fuel like you normally do
  • pobalita
    pobalita Posts: 741 Member
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    @tcunbeliever: do you think I need to eat any extra carbs tonight (maybe it's too late?)? I'm on the heavy end of ketosis and I assume my glycogen is pretty low.

    Also, assuming low glycogen, should I eat more during the run? Don't want to try to figure that out by actually getting to the point of "crashing".
  • tcunbeliever
    tcunbeliever Posts: 8,219 Member
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    you probably should eat 300 - 400 carbs tonight to replenish glycogen stores...and then you will probably be fine tomorrow with just a cliff bar, or you might not even need it because in theory you will store more glycogen after running out than you used to when you had carbs all the time
  • JodehFoster
    JodehFoster Posts: 419 Member
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    I'd be concerned w/ digestive issues eating that many carbs all at once after keto (it would go right through me or cause distress in my guts), esp since the run is tomorrow. I would've started a couple days ago gradually, or maybe start out eating them slow tonight & see how it goes.

    Good luck w/ the run!
  • sijomial
    sijomial Posts: 19,811 Member
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    At least prepare for the worst by carrying a phone and an isotonic carb gel. Are you running alone or with someone?
    Bonking (I'm an old and slow cyclist...) can happen very suddenly and in a confused state you don't make the best decisions - I certainly didn't!!

    Can't offer any fuelling advice as my adage is race how you train - it's in your training preparation when you needed to experiment.

    Best of luck and hope it goes well.
  • janejellyroll
    janejellyroll Posts: 25,763 Member
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    JodehFoster wrote: »
    I'd be concerned w/ digestive issues eating that many carbs all at once after keto (it would go right through me or cause distress in my guts), esp since the run is tomorrow. I would've started a couple days ago gradually, or maybe start out eating them slow tonight & see how it goes.

    Good luck w/ the run!

    Yes, I would be nervous about any big dietary change the night before a race.
  • mitch16
    mitch16 Posts: 2,113 Member
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    sijomial wrote: »
    At least prepare for the worst by carrying a phone and an isotonic carb gel. Are you running alone or with someone?
    Bonking (I'm an old and slow cyclist...) can happen very suddenly and in a confused state you don't make the best decisions - I certainly didn't!!

    Can't offer any fuelling advice as my adage is race how you train - it's in your training preparation when you needed to experiment.

    Best of luck and hope it goes well.

    ^ Good advice--it's pretty much too late now to change anything up, and even your tried and true could cause major issues because of the keto.
  • pobalita
    pobalita Posts: 741 Member
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    mitch16 wrote: »
    sijomial wrote: »
    At least prepare for the worst by carrying a phone and an isotonic carb gel. Are you running alone or with someone?
    Bonking (I'm an old and slow cyclist...) can happen very suddenly and in a confused state you don't make the best decisions - I certainly didn't!!

    Can't offer any fuelling advice as my adage is race how you train - it's in your training preparation when you needed to experiment.

    Best of luck and hope it goes well.

    ^ Good advice--it's pretty much too late now to change anything up, and even your tried and true could cause major issues because of the keto.

    Thanks. I won't be alone. There will be at least 100 other runners and it's two 6.5 mile loops. My son is running as well. He's way faster than me, but if I don't show up in a reasonable amount of time, he or other race staff will look for me. I've done this course multiple times so, other than the change in my diet, there won't be any likely unkowns. I always carry gels and will carry a couple extra this time - I bonked even with a mid-run gel on the 8 miler a few weeks ago.

    I agree about racing how you train and hate being in this "in between" place. I have a near 3-year streak of at least one half marathon per month and don't want to break it even if it means a miserable half marathon or two until I get the new diet in a more solid place.

    I hadn't considered that carbs could cause stomach distress - thanks to those who brought it up.
  • sijomial
    sijomial Posts: 19,811 Member
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    Very nervous of offering "advice" as keto is well outside my personal carb monster experience but one thing to consider is carbs little and often rather than gulp 28g of carbs in one gel shot.

    The keto / glycogen depleted state complicates things with hydration as well - if you suddenly take on a load of carbs your body will try to store excess carbs not immediately used along with x4 the amount of water.
    Much easier for cyclists to drink/feed during an event of course but I normally have my gels in my water rather than taking them "neat".

    Impressive streak you have there, can see why you are determined to keep going.

    PS for another time....
    Some research required into carb timing around training / events or maybe CKD?

  • pobalita
    pobalita Posts: 741 Member
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    sijomial wrote: »
    Very nervous of offering "advice" as keto is well outside my personal carb monster experience but one thing to consider is carbs little and often rather than gulp 28g of carbs in one gel shot.

    The keto / glycogen depleted state complicates things with hydration as well - if you suddenly take on a load of carbs your body will try to store excess carbs not immediately used along with x4 the amount of water.
    Much easier for cyclists to drink/feed during an event of course but I normally have my gels in my water rather than taking them "neat".

    Impressive streak you have there, can see why you are determined to keep going.

    PS for another time....
    Some research required into carb timing around training / events or maybe CKD?

    Agree. Based on what others said, I was thinking half a gel a couple times instead of one all at once. (Even when I'm not keto, they sometimes upset my stomach.) Or, a dilute energy drink.

    I understand about the glycogen storage. I used to run marathons and ultras (had to slow down because of asthma) and would gain 4 to 6 pounds almost overnight when carb loading. It was gone after the run.

    Just looked at CKD. Thanks, so much! This looks like what I might need for pre-event prep and I'll do some more reading. Just wasn't sure how to do it. This is why I love MFP.
  • speedingticket
    speedingticket Posts: 73 Member
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    pobalita wrote: »
    It's a trail run, so I'd be happy with an 11:00 - 12:00 min pace. 2:30'ish? (I'm old and slow.)

    Okay, half way sounds like a good time to take some carbs, if that's when you would have taken them before too. Just watch out for gut rot....personally I would rather bonk than have the runs, if the race were a little shorter, but if you might be out for an hour or longer feeling like rubbish, then it's probably worth the risk. At least with trail races nice toilet spots are always easy to come by.
  • Mr_Knight
    Mr_Knight Posts: 9,532 Member
    edited January 2018
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    If you're good at 3 miles and bonked before completing the 8 mile, you can estimate your calorie shortfall. Let's say the bonk happened at mile five, three miles worth of calories short. You want to do a half, add another 5 miles on top of that, for a total of 8 miles worth of calories.

    We're assuming glycogen stores are approximately depleted - if they're not, that'll be a bonus, not a penalty.

    So your calorie shortfall is roughly 8 miles * pounds-bodyweight * 0.65. If you're 135 pounds, that's ~700 calories. You're pulling down about half of that pre-race, so if you pull in another 350 during the race, you should be ok.

    BUT. The problem is body can only metabolize so many calories/hour, especially when being pushed physically. If the pre-race booster shot is at least 90 minutes before the the event starts, we can discount that, it'll be processed in time. At a 12 minute pace, if you get it into to you by the 1:45 point, you should be ok on the in-race fueling.

    All numbers approximate. Watch out for the assumptions. And good luck!
  • Orphia
    Orphia Posts: 7,097 Member
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    Normally for a HM (I've done over 25), I'd say carbs/gel pre-race, and around 8-10 km mark, then more at 13-15 km.

    Have you used gels with caffeine? I'm having good results with those. They seem to give me fresh legs.

    As for your keto, I'd make sure to hydrate extra-well in addition to the above. Start now. It won't matter if you need the loo during the race. The main thing is to finish the HM. Good luck!
  • richardgavel
    richardgavel Posts: 1,001 Member
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    If you end up gelling, I would take it in slowly with good hydration. Maybe half at package at a time instead of a full one.
  • speedingticket
    speedingticket Posts: 73 Member
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    I am assuming the OP has done her race now. I think we are probably opposite sides of the world, though, so I can't figure out the time difference...hope it went well!!
  • MichelleWithMoxie
    MichelleWithMoxie Posts: 1,819 Member
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    JodehFoster wrote: »
    I'd be concerned w/ digestive issues eating that many carbs all at once after keto (it would go right through me or cause distress in my guts), esp since the run is tomorrow. I would've started a couple days ago gradually, or maybe start out eating them slow tonight & see how it goes.

    Good luck w/ the run!

    This. I hope it goes well for you today!
  • AnvilHead
    AnvilHead Posts: 18,344 Member
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    pobalita wrote: »
    ...I hadn't considered that carbs could cause stomach distress - thanks to those who brought it up.

    I don't run halfs, but fwiw, I did keto about 15 years ago and it made for some very interesting stomach/digestive issues when I'd suddenly introduce carbs back in. I quickly learned to never be further than waddling distance from the nearest bathroom when I did that. Good luck with your half, hope it worked out for you!
  • fitoverfortymom
    fitoverfortymom Posts: 3,452 Member
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    Just checking in to see how you did!

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