Sunday, 13 July 2014

LCHF and distance running.

As I have mentioned previously one of the reasons I got interested in the LCHF diet is the possibility that it could be beneficial to distance running; this is what gets me interested as I am getting older and the possibility that I could carry on for a few more years at a decent level is exciting.

So I ran my first LCHF marathon back in March and it was all easy enough. I like the food and as you may have read previously I was able to train just as long and as hard as I have done before. The London Marathon and the South Downs Way Relay were to follow and I was hoping to take a close look at fuelling and energy levels when running for more than a couple of hours. But then I picked up a minor injury and have had a couple more since then ( I should add that these were related to skiing and mountain biking, not running). As a result I have not really been able to study this subject in great depth yet.

But it is an interesting subject nonetheless and so here is post number 1 on this subject.

How long can we keep going for?

Mention the word Marathon to a novice runner and a few ideas will come to mind; such as ‘why?’, or ‘26.2 miles!’, or ‘Hitting the wall’. The last of these is the one that strikes fear into the hearts of most runners.

Hitting the wall is simply another description for running out of fuel. Most of us only have the capacity to store enough glycogen to run for about 2 hours.  This is why we generally carb-load before a marathon, to fill the glycogen tank up to the top. Refuelling in good time ensures that we don’t hit the wall and so long as we have done the training we should complete our big run. We learned this back in the eighties and Lucozade and Gatorade have made a heck of a lot of money ever since. Clearly finishing a marathon depends on refuelling, or to put it another way, on consuming sugar.

So how did marathon runners manage to train for and run marathons (often very quickly) before the advent of Gatorade?  Simple, their bodies had adapted to burn fat as well as glycogen. They trained hard and in the absence of carb-gels and carb-drinks their bodies became rather good at switching from carb-burning to fat-burning when the need arose. Most mere-mortals do not train this hard, and if we are on a traditional (and NHS recommended) high-carb diet, we will need to take on fuel on our long training runs and we will rely on fresh fuel (carbs) on Marathon day.

LCHF runners train our bodies to burn mostly fat, with a small proportion of carbs. So, given suitable training we ought to be able to keep running for longer; much longer, without the need to refuel in the same way.

So how far can we go? And how fast can we go?

Dr Peter Attia is an elite athlete who has been testing these questions for some years, recording his performance on both low-carb and high carb diets.

 As you can see Peter is pretty serious. He has determined that a suitably trained athlete (himself) can keep going all day long so long as he doesn’t run out of carbs. Clearly the smaller the percentage of carbs being burned the longer we should be able to run for. A key point is that most of us can regard our fat stores as effectively limitless for these purposes.

We all burn fat as well as glycogen. The point at which we switch to burning more glycogen than fat has a profound effect upon how long we can run for before hitting the wall; the earlier the switch the sooner we run out. Dr Attia found that on a high-carb diet this switch occurred at a heart rate of 104, or 33% of his maximum output (or VO2 Max). When in ketosis (on a LCHF diet) the switch came at a heart rate of 162, this being 84% of his VO2 Max. Don’t forget that he is an elite athlete!

The diet brought about more than this simple change (note that his maximum output had lowered), but even though his VO2 Max had decreased by 12% with the change of diet he was now able to use his glycogen stores very much more efficiently.

After tests both cycling and running Dr Attia has figured that when he is working at his ‘all day’ rate he is working at about 60% of his VO2 Max. On a high-carb diet this required 95% of energy to come from carbs. On a LCHF diet with his body in ketosis this required just 22% of energy from carbs (or strictly from glycogen). So buy lowering the requirement for carbs he is able to go for much longer before running out.

Another aspect of high-carb fuelling is that when exercising for more then 1-2 hours our livers simply can’t process enough carbs per hour to keep the tank topped up. The normal limit is about 50 - 60 grams (or 200-250 calories) per jour.  There are 4 calories per gram of carbs; hence the need to take on carbs early in a run, and keep topping up the tank regularly.  If you leave your refuelling until you feel tired and you are running at a rate that requires about 800-1000 calories per hour then it will quickly be too late for consuming more carbs to be of any help. Here I must give credit to Sarah Rowell. Not only is she the author if the great book “Off Road Running”, where I first learned about trail and fell running and nutrition; but she was also the record holder for the Beachy Head Marathon for 5 years after trouncing all the men in 1986.

How many of us have wondered “what might have been” as we tread that painful last 8 miles towards the finish line with no carbs left but a reserve tank full of fat gagging to be burned? When we decide to run long on carbs, we are all treading an unavoidable path towards that same wall.

Now consider what those last miles might feel like if we were only consuming 25% of our calories (250 grams per hour) from glycogen. We could keep the glycogen tank full as long as we like if we re-fuel appropriately.

Is it any wonder that so many ultra distance runners are using a LCHF diet?

My attempts to replicate this investigation have so far been thwarted by a dumb show-off-dad injury and some bad luck. However I can attest to the fact that running the Hassocks Sport Relief Charity Marathon on LCHF did not leave me feeling even slightly drained or hungry. I ate eggs and bacon before the run and just a couple of cups of soup during the run. But I was not going particularly quickly (I averaged about 6.2 mph on a heart rate of about 130) - nowhere near 60% of my VO2 max.

So I thought I’d call upon the experience of Marina Bullivant. Marina is becoming a bit of a legend around here, having run all 5 Brighton Marathons. After the 4th run she switched to a LCHF diet, lost a stone and a half and then proceeded to beat her PB from 3 years earlier. She has run 3 Marathons so far this year on LCHF, each harder than the last. I asked Marina a few questions about the way she eats and runs:

Q: How long have you been on the LCHF diet?
A: Since June 2013.

Q: Can you estimate how many grams of carbs you eat per day on average?
A: Malcolm, I haven't ever calculated what this might be, or even thought about it!

Q: When you run for over an hour do you use any kind of food for fuel? –
A: I only really fuel for races, and then only half marathon and above.  SDW Relay - sausages, breakfast muffins (eggs, cheese, veg, bacon), cheese, nuts - deviation is Janna's homemade barrabrith (fruit teabread with loads of butter!).  Brighton Marathon I took a couple of the gels they were handing out and wished I hadn't - got stomach pain - stupid thing to do as I never take them normally!  And still got cramp in my calves!  I now take  salt/electrolyte capsules with water on runs over 1.5 hours, no calf cramps so far!

 Q: What is your average mileage per week? Has this increased on the Diet?  
A: I'd have to have a look at my records - it has probably increased since June 2013, as have been running longer races, so training further.  but, as you will see in answer to question below - definitely faster.

A detailed conversation revealed that the average has risen from about 40 to about 50 miles per week.

 Q: What is the longest that you have run for using this regime? –
A: Three Forts Marathon - 27+ miles (May 2014 - my longest ever run). 

Q: After a long run how long does it take to recover before you would run again?  
A: 24 hours!  

Q: Is this recovery rate a change from your recovery rate prior to the diet? 
A: And thinking about it, this was probably not the case before, would say that previously 2-3 days.

Q: What are your 5K and marathon PBs? (here I am looking at the difference between the two paces – what is achievable on LCHF).    
A: 5K  22.32 (June 2014).  Marathon 3:46:36 (April 2014).

I particularly liked Marina’s answer to the second question - she is not counting carbs at all. Not very scientific though, so I quizzed here a bit further and I reckon that she eats about 60  grams of carbs per day, apart from a bit of a blow-out with a roast potato or two with dinner on Sundays which puts her up to about 120 for that one day.

Assuming that Marina is running at close to her VO2 max for a 5K at 8.4 mph, and she runs a marathon at 6.9 mph then her marathon pace is 82% of her VO2 Max.

There is a big difference between Marina and Peter’s all-day rate VO2 Max 80% and 60%. This is likely to be because Peter is an elite athlete with a very high VO2 Max in the first place, whereas Marina just trains for and runs long distances. I think I should have mentioned that this is not rocket science but we can see that Marina is achieving something rather special here; she has lost weight and she is getting more efficient at distance running. Her recovery rate in particular is amazing; she trains the day after running a marathon. Now I never managed to do that!

There is a suggestion that LCHF leads to less inflammation in the body. This is critical in the case of atherosclerosis (inflammation of the arteries) as it means that we are less likely to develop heart disease on a low carb diet than on a high carbs one. You may recognise this as the subject of my earlier posts ( ). But this also has a bearing on the inflammation on our bodies caused during training; if there is less soreness from training then we should recover quicker and can train more. This is what Marina seems to be finding.

This experience is mirrored with another correspondent Simon, a GP on the LCHF diet, who states that
Since going low-carb I seem to get less muscular aches in my legs the day after a run; but possibly this is just due to the passage of time rather than my diet.

Simon has seen improvements across the board, not just for endurance running:
I had thought that my fastest times were behind me. I started reducing carbs 18 months ago and within a matter of 2-3 months was running faster. I have lived the LCHF lifestyle for over a year now and have never run as fast.

Last month I set a lifetime best over 5K and have improved my time over 10K by nearly 2 minutes. My passion is fell running and have seen my times tumble compared with races a year or two before and not by small amounts - 11 mins off a 14 miler in Pendle and 32 mins off the Three Peaks Mountain Marathon. These are races I have done several times before so I have a good idea of what I am capable of running.

This all suggests that LCHF may indeed assist recovery and perhaps even improve performance. My own memories of the Three Peaks Fell Race centre largely around climbing Ingleborough splattered with sticky pink energy drink.

I was also hoping to write about the South Downs Way Relay on LCHF. This 6-person team event covers the 98 miles of the SDW in somewhere between 11 and 14 hours with each team member running 3 legs at close to threshold speed.
                                                                         (The Arena 80 Vets team from 2008)

This race presents particular challenges with regard to fuel – you have to get plenty of fuel down in order to keep going all day, but not so much that you might get a stich from running too soon after eating. Many runners find it hard to get food down at all after a hard run and that compounds the problem.

I have run the event three times for my club Arena 80 and we have come third, second and first in the fiercely contested vets category. On each occasion I have gulped down a pasta, tuna and veg salad the moment I finished each of the first two legs and drunk energy fuel liberally. Luckily I can eat just about anything anywhere (the cook ran out of popcorn and bacon when I was climbing Kilimanjaro), but I still felt worried about energy all day long. Other runners were clearly having bigger problems and the changeover stations were strewn with messy corpses and discarded energy gel packets.

I missed out on the relay due to injury this year, but Marina was invited to join a ladies team from Hurstpierpoint. And so she was able to road-test the LCHF diet. In short it was a doddle. While several of her team-mates suffered from stomach cramps and lack of energy Marina ate some egg&cheese muffins, cheese, nuts and some fruit tea-bread washed down with a good amount of water & salt tablets. That’s all. She reports feeling satiated and strong all day long.

Now as I said earlier Marina is superbly adapted to distance running, but as a first-timer in this gruelling event she did appear to shine.

The key lesson here for LCHF runners is that if we want to run all day long then we can do, but we still need to eat a few carbs to keep the tank full. Marina had some bread. I might eat some flapjack or drink a malco-pop; but we do not need to worry about hitting the wall if we are fuelled by fat.

P.S - If you'd like to read more, including the answers to the question "How fast can I go?" then have a read of my later posts describing fuelling, pacing and finally a PB in one of the hardest marathons in the UK.

Some further reading and inspiration:

2 times Triathlon world champion Jonas Colting is on LCHF

Tim Olsen, the winner of the 2012 and 2013 Western States 100 is on LCHF

Sami Inkinen, a persistent winner of Ironman races is on LCHF. He also writes about his performance here He is currently rowing from San Fransisco to Hawaii to raise awareness of the dangers of sugar.


  1. Hi Malcolm. Thanks for a great read. Where can I get the Fueled by Fat tshirt pictured in your blog? Thanks

  2. Hi Helen - sorry for the lack of reply I must have missed the auto-email. The shirt is a modified version of the standard shirt that we distribute to members of our community running group "We Run Hassocks". If you would like one you should be able to order it on-line from my wife's company website here: order the size you need and I will make sure that it gets the FAT logo.
    I'm glad you liked the post.

  3. Hi Malcolm - I just stumbled across your blog as I was looking for answers as to whether LCHF would help me with my shorter races.An interesting read.
    I have just completed my first fat fueled marathon (london)2:56:53 which gave me a good understanding on how well fat fueling can work for endurance athletes. I am hoping to do a 6hr ultra in june to really test the effectiveness of fat fueling..Just with people would realise being sugar dependant is not the way forward..
    Iain Love