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I've signed up for a 3.5 mile evening run/race (starting at 7:10pm) which is this week.

I've been IFing through breakfast and lunch for the last few weeks (and have done so for a great number of weeks in the preceding 5-6 months), and am considering doing the same on the day of the race. So I'll eat a nice, regular fat/protein feast Wednesday night, and then probably nothing until after the race.

I've done plenty of endurance activities/training after 'fasting' in the range of 4-8 hours, but never for nearly 24 hours.

Am I crazy, and should probably eat something for lunch the day of the race?

Edit: This is the night before, I've opted to go with some starch with my dinner tonight, taken from a 'recipe' posted as an answer to another question. We'll see how it goes. I may (foolishly?) get some kind of workout in tonight, though.

Edit 2: So I didn't do another workout the night before, but ate some more fat (coconut & greek yogurt, I think). I fasted all day, ran my race. Couldn't really gauge how I did since I started way back in the pack (of 23,000 runners/run/walkers) and spent a lot of time in the first mile wading through slower bodies. After that, I picked up a little more speed, and had plenty of gas in the tank for a surge the last mile - the walkers ahead of me had thinned out (or I passed them). I felt great! I went back to our team tent and was thoroughly disappointed in the food they offered, so I didn't have anything. I made my way back home, and finally nearly 2 hours after I finished I had a half pound of grass fed ground beef, 3 pastured eggs fried in coconut oil, coconut chips with cocoa, some cottage cheese, and a larabar. I felt great, and feel good this morning. 24 hour fasted running is just fine in my book!

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In case you need more info regarding my usual diet during IFing through breakfast and lunch: my normal dinner during these times is primarily protein and fats. Then a few hours later I'll do either strength or endurance training. After endurance training, I'll eat more fat and protein. After strength training, I'll eat a ton of carbs as either rice or potatoes, and sometimes some fruit. – Casey May 24 2011 at 16:58
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 If you like running in the afternoon/early evening, there is a 5K @ 4pm down at Balmoral race track next month. You get to run around the track, then stay to gamble! I'm running it with some of my girls. – sherpamelissa May 24 2011 at 17:30
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 No way I could do that with the kids' nap schedules. I also think I'm already double booked on the 11th! :) – Casey May 24 2011 at 17:55
hate to be stupid, but what is IFing? – Sue Holt May 24 2011 at 19:10
Intermittent Fasting :) – Casey May 24 2011 at 19:46
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8 Answers

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I run 5k every other day or so and have recently tried running fasted. To my surprise, I did not feel much different at all, even somewhat better in the 2nd half of the run. This is really fasted, like no food for 18-24 hours. Getting warmed up is a little rough and the first mile or so can be a bit choppy, but once my heart rate is up and I'm in stride, I feel "lighter" and have more spring to my legs.

When I get back, I have about 15 minutes to eat something or I feel like I'm going to fall over, and there is temptation to eat anything so a Paleo-friendly snack should be handy. Last time I was a bit desperate and had a large glass of whole milk and a banana and felt great afterwards. Also make sure that you have plenty of water before and after.

Another time I ran a jog about 1 mile and did about 15 minutes of sprints (about twelve ~50 yard sprints with recovery time between). The whole time sprinting and recovering I felt great, but again when I got back I was seriously in need of nutrition.

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Thanks - I don't rule out dairy or bananas in my diet, so that's OK by me. There's likely to be all sorts of SAD options in our post-race tent, I'm just hoping there'll be something I can eat. Excellent point though, I'll have to make sure I bring something along I know for sure I'll be able to eat. – Casey May 24 2011 at 19:49
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 Don't rely on anyone else to provide anything, bring whatever you want to eat with you then you'll have no excuses.. I'm a fan of fasted all the way. Good luck.. – Alan May 25 2011 at 8:12
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 Most high end endurance coaches, trainers, strength and conditioning coaches, etc. say that any event under an hour requires no specific nutrition (i.e. no carbo loading) prior, no carbs during, and in most climates, no water during. I think when we get into the realm of 2+ hour endurance workouts, then it's time to start looking to pre- and during-event nutritional needs, but for anything under 10k-ish, I think it's not a question. If you felt great when you were done, that's all the answer you need! – Scart Jun 23 2011 at 17:03
@Scart - that sounds like a good rule of thumb. However I'm sure they'd (mostly) all agree that not eating for 24 hours prior to an event is probably a Bad Idea. – Casey Jun 23 2011 at 18:15
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I play soccer a few times a week. Often times it is in the fasted state. I have noticed an uptick in endurance and play while fasted. When I have back to back games, or two in one night, I eat a big lunch with some starch first.

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 I also play soccer fasted, and notice no dip in performance. Sometimes I even play better with no food in my stomach. – ROB May 25 2011 at 0:04
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I did my two 5ks fasted, not on purpose, but it just kind of happened. I don't like to eat before a run or I burp up the taste of it the entire time I'm running. (Yes, TMI!) I did pack some salted nuts (which I rarely eat) and some mini cheeses and apple slices that I ate pretty much as soon as I got in the car after the 2nd race.

So, I had dinner the night before, probably around 6/7pm, then ran the first race at 9am, had some coffee and did the second race at 2pm. I was fine and I actually don't IF very often.

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Super helpful, thanks! – Casey May 24 2011 at 17:03
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 I had a similar experience. I ran a 10k a few weeks ago after a roughly 12 hour fast. Not a big deal as long as you have a lot of nice glycogen stored up from a previous meal. – Nick A May 24 2011 at 18:12
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As with most things, it depends. I think it would be fair to say for most competitive runners 3.5mi, is more or less, a balls to the wall all out effort. HR should be greater than 90% of MHR for the duration of then event. At this intensity you'll be pretty much burning pure glycogen as fuel. But only for around 20min, depending how quick you are. :)

I think you'll be fine if you IF then race, especially if you include a nice hit of carbs in your meal the night before, to bump up glycogen stores.

However, will that lead to maximum optimal performance? Hard to say. Personally I would have a meal that included starch 4-6 hours before the race. Though the benefits of that could simply be more mental than anything, in having the confidence of knowing that I had plenty of fuel to run my best.

If this is going to be a weekly thing for you, I would play around with both IF'ing and not and track your performances. A bit of N=1 experimentation. Given the short duration of the event you may find it's really much of a muchness.

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Good food for thought (hahaha). This particular event is just once a year. My normal training routine(s) only let me have a longer run on the weekends, midday, during the kids' nap. – Casey May 25 2011 at 13:25
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Train Now Live Later had several posts about doing certain races while fasted. Type "fasted" into the search block on the upper right and you'll see a few results right away for various races that he did last year.

http://trainnowlivelater.blogspot.com/search?q=fasted

P.S. Good luck, and maybe edit the question with a sentence or two letting us know what you did and how it went?

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Ah yes, I had totally forgotten about him! Thank you for the reminder! – Casey May 24 2011 at 19:46
Oh, and yes - I'll totally update afterwards. Even with the (currently) mostly positive input so far, I'm still a little up in the air. – Casey May 24 2011 at 19:54
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Bad idea, unless there is something you like about high cortisol.

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I appreciate your input :) – Casey May 24 2011 at 19:47
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Fasted training during your training period is beneficial in fact a lot of elite runners doing doubles will run their first run fasted before breakfast. Before a race though they eat.

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I've been doing doubles lately. Not 2 run workouts, though - since I'm training for triathlons, my evening workout will be either swimming or biking (with or without weights). My lunchtime runs and sprints are now all fasted from the night before. – Casey Jun 23 2011 at 18:10
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It depends on how fast you run. A 3.5 mile race is pretty short so either you guys are gonna run real fast or it's probably just for fun. If it's competitive real fast I'd say not if you want to win. Either way you should at least carb up the night before.

I surf everyday fasted which includes biking/skateboarding to and from the beach for 10 miles and surfing for 3-6hrs, I have bouts of high intensity but I eat 500+ grams of carbs everyday to keep my muscles glycogened up.

If you do it fasted drink lots of water because good hydration keeps cortisol low.

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The event has come and gone, but I appreciate the input! I ended up fasting, some carbs the night before. I'm now doing a lot more training fasted - it's really great :) – Casey Jun 23 2011 at 18:12

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