I personally couldn't hang with a low-carb paleo approach when i was distance running. I'd experience the same impaired performance that Stephen mentioned. However, I think you really have to take the time build a strong aerobic base to become an optimal fat burner to preserve glycogen stores more efficiently. Here's a couple links that might give you some insight on paleo endurance strategies:

http://www.marksdailyapple.com/jonas-colting/

http://robbwolf.com/2010/05/31/paleo-and-ultra-endurance/

Honestly, I've been doing endurance running for a couple of years, and have run a few races this year already (two half-marathons and a couple of 5K's and 10K's). I haven't really changed up anything in the Paleo Diet. I know there's the "...For Athletes" book (I own it) but I have a hard time wrapping my head around eating more carbs.

I actually have found that practicing IF in the mornings (so I don't eat until noonish anyways) kept me from being hungry the morning of a race, and then I just had coffee a couple of hours before the run. Scarfed down some good clean foods post-race and then ate normally the rest of the day.

Results may vary, but this has been my experience.

I have been training for my first Half-Ironman triathlon, and I swear by sweet potatoes. I eat AT LEAST one a day. For me, those are the best carbs for long workouts or races.

Search around on MarksDailyApple.com he is a former endurance athlete turned Paleo dieter and has written a lot on the subject. You may need to adjust your diet a bit including adding some carbohydrates before/after your long workout days (> 1 hour). You also may need a little longer (4 weeks +) to adapt to the diet. I believe that's what the research by Dr. Phinney finds.

Curt

I've tried a few of the suggestions here and did a bit more research too.

Magnesium supplementation at 400mg/day did not solve the issue, though I understand that sufficient magnesium helps with potassium retention. Adding some extra carbs did not help either.

What solved my feeling of crampy, unresponsive muscles was 400mg of potassium gluconate (suggested in the Eades' book The 6 Week Cure). I didn't expect it to work quite so well given that the US RDA of potassium is a whopping 3.5 grams and I already use potassium chloride liberally in cooking.

I have had to adapt and drink carbs during bike rides lasting longer than 1 hr because I would fatigue and feel weak and dizzy after about 45 minutes. I now drink between 1/2 and 3/4 of a small bottle of PowerBar Endurance (half of what I used to drink before paleo), and supplement with a homemade bar (cuisinarting mixed nuts, dried fruit, coconut oil) and a little pemmican, if ride is longer than 2-3 hrs or if I ride on an empty stomach. It is early in the winter, so I have not had super intense rides at race pace yet.

Check out Dr. Steve Phinney's work on this. http://www.meandmydiabetes.com/2012/01/04/steve-phinney-low-carb-shows-benefit-for-athletes/

Here's a great podcast with him. http://www.meandmydiabetes.com/2011/04/14/steve-phinney-low-carb-preserves-glycogen-better-than-high-carb/

Here's his pemmican take http://www.meandmydiabetes.com/2010/03/23/steve-phinney-on-pemmican-and-indigenous-diets-will-become-public-in-2-weeks/

Have you seen The Paleo Diet for Athletes?

"Born to Run" features ultramarathoners who run mostly on carbs.

I wonder what how much power is available from the fat-burning pathways -- what level of continuous exertion can a ketoadapted, body-fat-fueled athlete sustain, under conditions of zero dietary carbs and glycogen exhaustion?

Is it possible for the guys who do 24-hour runs, or 100-mile runs, to do it on stored fat, or are dietary carbs pretty much essential to sustain, say, a 10-minute mile?

In my prior post of Jan 7 2012, I noted that after 45 min of intense cycling I would lose stamina. I had been paleo for about 3 weeks then. Eventually I pushed through and eliminated the carb drinks altogether, only drinking water; for longer than 60 minute rides, I do not cargo-load and only eat 1 Larabar per 90 minutes of riding, about 15 to 20 grams of carbs per hour, plus all the fat and protein in pemmican that I feel like, usually about 15 grams of fat and 8 grams of protein per hour. I completed my first bicycle race March 11, very hilly 110 miles and found, to my surprise, that I was able to maintain intensity with only the usual fatigue. So indeed, your body can get used to burning primarily ketone bodies, metabolized by the glucagon secreted by your pancreas from fats and protein, and also by burning stored glycogen. I am still experimenting…but it took me 4 to 6 weeks to make the full transition to a high fat/low carb diet and retain the same level of performance in competitive cycling.

Glad I came across this thread. I posted this: Different Diets for Aerobic vs. Anaerobic Exercise

today and haven't gotten any responses. My partner is also an endurance cyclist and he wants me to help him create a more nourishing diet that will help him lose some fat while keeping lean muscle.

I've been reading around the interwebz (although I have yet to read the above mentioned links) and I was thinking that it might be better to start him off with something very strict (the Whole30) rather than less restrictive. If he operates like I do, and I think in this case his might, the effect of this being like ripping a band aid off in one fail swoop might make more of a positive impact on what he's hoping to attain -- and then he can choose to continue to eat Paleo or even try IF.

He's looking at me to do all the research (and most of the food prep) here. I'd love to get the whole family Paleo and if he's on board it'll be a lot easier to convert the kids (one of whom is the pickiest eater on the planet).

But I don't know. I could use some feedback on my original post. Hoping ET might weigh in. :)

Read "The Art and Science of Low Carbohydrate Performance". I have been adapting to a ketogenic state for 4 weeks now (as measured by nova max plus blood ketone monitor) and I am getting faster. Keep carbs to less than 50 grams per day and eat 75-80% fat. My best 5k is 16:37 on a SAD diet. I believe that I will be able to match and hopeful best my 5k PR. I ran a time trial last week in 17:50 on my 3rd week of a ketogenic diet.

Timothy Olsen, smashed the Western States 100 Ultra Trail, running on fats. Destroying all the carb fueled athletes. See podcast link on this page :

http://www.thelivinlowcarbshow.com/shownotes/7302/642-ultramarathon-runner-timothy-olson-thrives-on-a-low-carb-diet