Fasting and Endurance Sports?

Read time: just a quick note

Although I haven’t looked deeply into research on intermittent fasting and its effect on endurance performance and recovery, here’s what the folks over at LetsRun forum is saying about IF.

I know a friend who completed a half marathon with his best time while in a fasted state. Of course it’s just anecdotal, but I have to believe that the body not only adapts to nutrient intake and intake timing, but also that the increased fat metabolism while in a fasted state may contribute to sustained aerobic output.

I’ll look into this relationship in the future, but for now this is something to chew on (or not, if you’re fasting).

This entry was posted in Dietary Habit, Exercise and Physical Activities and tagged , . Bookmark the permalink.

14 Responses to Fasting and Endurance Sports?

  1. Rob says:

    I am running a 5K race tonight at 6:30pm. I fasted yesterday from 11:30am until today at 10:30am except for a small bowl of Breyer’s ice cream last night about 9pm. I broke the fast with a caesar salad and baked chicken wrapped with bacon. I’ll eat a banana and two scrambled eggs about 2 hours before the race.

    I normally will fast 16-18 hours and then run a 4-6 mile training run at about 8 min mile pace. I love running in a fasted state. I feel so much better and I don’t get that need to use the bathroom feeling when I push myself to the limits.

  2. Jane says:

    I always train fasted. I don’t even drink water before I am out the door for a running session. I also hike fasted. And by hiking I don’t mean walking or power walking, I mean hiking from anywhere from 4 to 6 hours or even more in alpine conditions.

    I feel best fasted and my endurance workouts are great. I enjoy them. I tried running and hiking with food eaten before, but I was nowhere near the condition I am in when doing fasted sports.

    Fasted endurance sports = THE BEST

  3. Johnny says:

    Good comments so far.

    I would love to see more comments and feedback from those who participate in endurance activities (running, hiking, cycling, etc.) while in a fasted state.


  4. Dan says:

    I’ve run marathons for about 4 years now. I just did my first (Orange County ’10) while using IF during training. There were other changes I made in my training, so I can’t say that IF made the difference, but I set a PR (3:38). I eat a somewhat-Primal diet, and I think that has helped a lot, too. During training, I won’t eat before or during runs (including long runs), but during the race I ate a GU pack at roughly 15 miles. I have to say, it tasted pretty nasty and I didn’t feel so great; I don’t think I’ll do that again. When I feel thirsty, I drink water or an electrolyte mix, but I generally don’t drink for runs under 2 hours.

    When I first made the change, I felt the typical lack of energy, but this went away within the first ten minutes of the run, and disappeared completely after 2-3 weeks. Now, I almost never eat before a workout of any kind, including weights, hiking, and Ultimate, all with good results.

    • Johnny says:

      Check info, Dan.
      Thanks for sharing.


    • Jane says:

      Hi Dan,

      Maybe you want to try and eat some dates during your races. Or blend up some dates and as much water as you like to make dateOrate. Fill in a running flask and drink during race. That’s great, easy to prepare & digest & gives you energy.

      Good luck

  5. Rob says:

    I placed 3rd in my age group (22:55) and a trophy tonight! And I think I was near the top 10 overall. They had free beer afterwards which is always a plus. I am going to run my next 5K race in a fasted state at least 16 hours. I had baked chicken at 10:30am, scrambled eggs and a banana at 4:00pm, and then raced at 6:30pm. I had cramps on both sides the entire race and had to walk 3-4 times after the 2nd mile. mile 1 was 6:57, mile 2 was 7:04, and then it went downhill. I feel better when I run fasted (16 hours) in the mornings. The next one is in the evening too at a brewery – more free beer afterwards!

  6. Doug says:

    I’ve recently been reading about intermittent fasting, and I was wondering how it would work with ultramarathon training. I typically have trouble running even five mile without a fairly recent food intake, and it would be especially difficult for me to complete long runs in the 10 to 20 mile and beyond range with the restricted calories.

    I see that other runners have posted about training/racing with intermittent fasting, but what about us ultra runners? Is there is some adaptive process as the body gets used to fasting that curtails this need for fuel?

    I should add that I ran five 50k’s, a 50 miler and a 100k last year, but this year has been a year with back/sciatic issues that have resolved only in the last month. I’m now having trouble running 10 miles, which is a function of two things: Less training and more body fat. If I can figure out a way to use intermittent fasting to improve my running and drop weight, then I want to give it a try.


    PS: I’m turning 59 in December, but I don’t use age as an excuse!

    • Johnny says:

      Hi Doug,

      You should be able to use some form of intermittent fasting as a way to drop the body fat you might have gained, but you may want to experiment with intermittent fasting for running (in sub-ultra-distance running, that is).

      You can certainly IF around your training schedule, and it just takes a little bit of planning. But if you want to fast during your running, this requires experimentation. It may or it may not work for you.

      I’m not sure about the effect of IF on ultra-distance.

      And you’re right — age is relative!


  7. Dan Rivera says:

    In my experience as a cyclist, Anything 2-3 hours in length (depending on intensity) is entirely doable in a fasted state. It really depends on glycogen reserves, i.e. what you’re eating when you aren’t fasting.
    Eating during training, in my opinion, is entirely optional depending on your goals. I feel best when I start fasted, with coffee. Otherwise I never really “turn on” and slog slog slog through it. If I eat on the bike, its with the goal of maintaining an adrenaline fueled environment.
    If the ride is late in the afternoon, fruit works best for me. Maybe 200-300 calories half an hour before, and fuel as needed but never enough to take me out of that fasted feeling.
    I don’t care what anyone says; For me, food = relaxation, not energy.

  8. Özgür Simsir says:

    I`m have been on one meal a day for the past 2 weeks with only 800 – 1600 kcal a day, which i alway consume around 6 to 8 pm. In the morning I always do rope skipping for 40 min at a fast pace and afterwards I hit the heavybag for about 30 min. I also feel way more energetic and motivated during these High-Intensity Workouts than I would be in a fed state. I dropped about 10 Pounds in those 2 weeks and I just feel better than ever. Some people argue that HIIT during fasting is detrimental for performance but I personally have to disagree with that because I´m doing even better in a fasted state. Everybody who has any doubts about doing HIIT while fasting, I encourage you to try it out yourselfs to see how it affects you. Don`t let anyone tell you that this and that is wrong or bad, whatever!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s