Two things happened over the last fortnight to get me thinking about whether it is beneficial to convert to being low-carb if you are an endurance athlete.
The first was a question on one of my old posts from someone who wanted to know how I dealt with the problem of being glycogen starved while training in the context of having converted to a low-carb paleo diet. The second was a high-carb v low-carb debate that I frequently have with a friend of mine who is a long-distance runner (regularly competing in marathons, half-marathons and 10km races).
My personal experience of converting
For a long time after I converted to a low-carb diet I continued to be high-carb for the purpose of my weekly long distance bike rides, because it was easier that way. Eventually though, I decided that I couldn’t keep compromising my health. I knew it was possible to be an endurance athlete on a low-carb diet having read various testimonies. I’d also heard about Chris Carmichael, the professional cyclist and former coach to Lance Armstrong, who advocates a low-carb diet for athletes.
To convert, I found a period of a few weeks when I felt able to put my weekly long-ride on hold. Instead of a long ride, I went slowly round a local 30 mile circuit in a completely fasted state before breakfast. This taught my body to burn fat for fuel.
The first time I did it I felt horrid and ran out of energy about 10 miles from the end. Fortunately on a bike you can change gear and spin the pedals with minimal effort – you don’t go very quickly but you can keep going enough to crawl home. By the third or fourth week I could get round the full 30 miles and, although hungry, I had enough energy to work hard on the hill climbs. The subsequent benefits to my long distance rides were worth the effort.
The benefits of being a low-carb endurance athlete
The key differences that I saw have been noticed by others too, such as a pig-hunter who commented on Mark Sisson’s blog. I’ve listed below the biggest benefits to me.
- Not needing to eat as frequently – I can now survive on a snack every 3 or 4 hours when out cycling or walking, rather than needing to put in some food every hour.
- Not needing such large snacks – fat goes further than carbs, so I don’t need to eat as much when I do stop to eat. A handful of nuts or a square of dark chocolate can be sufficient where I would have previously needed a whole flapjack or banana at each break.
- Being able to keep going when I run out of food – it’s not pleasant, but if I run out of food I can keep going when I used to be left exhausted, sat by my bike at the side of the road. I will always carry some body fat, and I can burn that fat for energy in an emergency.
Feeling the benefits of a light-weight pack
Arguments in favour of staying high-carb as an endurance athlete
My friend, the long-distance runner, puts forward the following arguments in favour of staying high-carb which, from his perspective, are equally valid:
- When running it is difficult to digest most foods (due to the bouncing vibrations through your stomach) whereas a sugar glucose drink can go through the system with relative ease.
- There are psychological benefits from putting something sweet on your tongue, not just physical benefits. My only argument against this is that these benefits have been seen even when gargling the sugary liquids, so you don’t need to ingest them to get the psychological benefits.
- An organised run usually includes regular feed stations where they provide energy drinks and other sugary substances. With this in mind, why go through the unpleasant conversion process when you would then have to start carrying more of your own food?
The problem with advocating low-carb endurance training
Almost all of the success stories about being a low-carb endurance athlete are just that. Personal accounts. Most dedicated athletes play around with changing their diet but few will write about the change unless it was successful. So while we know that being low-carb does work for some endurance athletes we can’t extrapolate that it works for everyone.
Turning to science, there have been studies comparing low-carb and high-carb diets but when you are addressing something as fundamental as long-term diet it is difficult to do a fully controlled trial.
If you are comparing different groups of people (eg. comparison of a non-western tribe to a standard western population) there are too many other aspects that may skew the data, such as activity levels or genetic differences. Meanwhile, scientists have noticed that if people are asked to convert their diet to something that is perceived as “healthy” for a scientific trial, they will often make changes to other areas of life too, such as activity levels, because they feel healthy.
Make your choice to suit your preferences
My friend and I are unlikely to ever agree.
He has strong reasons for not converting. He doesn’t have a problem with the potential health issues from the high-carb foods that he consumes, he is concerned about trying to digest anything that isn’t in liquid form while running and he doesn’t need to worry about being able to carry his food since he is competing in races with food stations.
Personally, I am more concerned about the long-term health issues that could compromise my biggest life-goal. I also often have to carry any food that I want to consume and, when you are carrying 6 days of food on your back in a rucksack while crossing wilderness terrain, being able to carry less food is a benefit that outweighs everything for me. It’s also good to know that if I run out of food several hours from a food source (as happened once in the Cairngorms), I can keep going on reserve fat.
The important thing is to make your own decision based on your specific facts and circumstances and addressing the things that are of most importance to you.
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Low carbohydrate diets // May 31, 2010 at 15:03
[...] intake (thus leaving the body with no choice but to burn the fat it is already carrying), but the requirement for fuel when out exercising is reduced. As a great example, Chris and I can now get by each eating 150g nuts and 100g dark chocolate [...]
“While low-carb diets have their merits for a select population, a nutrition program higher in carbohydrates is much more appropriate for you as an athlete.” –Chris Carmichael’s Food for Fitness (Putnam, 2004)
Thanks for the quote. However I would have to disagree with using this as a catch-all for all athletes.
I’ve found that I have performed better than ever in endurance sports on a low-carb diet. I’ve also found that my performance is, so far, not particularly hindered in the gym either (though there is a possibility that my progress would be a bit faster if I took in slightly more carbs) and would put forward Robb Wolf as another example of someone on a low-carb Paleo diet who continues to lift weights.
There may be an argument for being higher carb if your sport is particularly sprint-focused where the body tends to call on glycogen reserves, however the body is perfectly able to adapt to burn fat for longer, slower, endurance output and can keep going for longer by relying on fat rather than carbs. I strongly believe that you need to look at the sport you are referring to and adapt the body and the diet to suit the particular activity.
I have been running for over 30 years. It has been my exercise of choice though I taught aerobics at a gym when that particular craze swept through.
I converted to a low-carb diet for health benefits while I was in the Philippines. I felt AWFUL for a couple of weeks. I even stopped my run one day while I was attempting to run 8 miles. However, I stuck to the low-carb regime.
I am happy to report that I am currently reaping the benefits. I wake up clear and ready to run. In 2 months, I have yet to experience any “lag” or feeling of fatigue on my morning runs, despite the fact that I only drink a cup of coffee with cream before exercising. I do not get hungry until about noon, eat a sizable meal, and snack in the evening as I am not hungry enough to eat a full meal. I have lost 10 lbs (now weigh 110) and have great energy.
Interestingly, I have always sort of run “low” in blood sugar requiring that I eat frequently (usually high sugared fruits, healthy crackers, etc) to thwart symptoms. Since converting, I have yet to have a feeling of “low blood sugar.” Interesting, eh??
So. . .I can only report how my body has responded to burning fat over quick carbos.
Thanks for sharing your experiences. This is exactly the sort of thing I have seen happening for my cycling and walking but I struggle to get runners to believe that it is possible to run without an endless supply of sugary drinks and snacks.
Any suggestions for what you would eat (low carb) during a marathon race?
Not having ever run a marathon myself I’m probably not the greatest expert on this. When I’m doing long distance walks (6-8 hours) I normally carry a large bar of 85% chocolate as an emergency provision which I have a few squares of if I’m finding it tough – that said, I didn’t eat any of it on my last holiday because I was content running off body fat and the protein, fat and carbs which I’d put in the night before at dinner. The pig hunter I linked to in this post doesn’t seem to eat anything at all all day either.
Somebody recently wrote to Robb Wolf and, reading through what he has written, he seems to have run a marathon fuelling on almonds and water. I certainly used to use mixed nuts for fuel on my walks when I still wasn’t able to go for the whole day running on the previous evening’s fuel input and body fat.
Depending on where you are on the fat-adaption process there may be an argument to put some basic carbs in partway through a marathon to get that extra boost (dried fruit broken up into small bits stuff which may be easy to digest – bananas?). However if you are already well adapted then you can probably afford to go for those high fat/lower carb options like nuts and chocolate. I would imagine that chocolate carries the benefit of having less digestion issues if you carry it broken up into quite small pieces and almost melt it in your mouth to a semi-liquid form before swallowing – avoids chewing and digesting – whereas nuts may be harder to handle while running.
You probably need to try a few things when training to see what settles most easily in your stomach and where you sit on the scale of fat-adaption.
Not sure how much help that is, but hopefully it’s given you some ideas of things to try out. Would be good to know what you eventually find works for you!
Thank you so much for all the tips. I am going to try a variety during my training and see what works. I’ll let you know.
According to exercise physiologists, training in a low-carb state causes two undesirable responses: 1. protein breakdown, 2. liberation of fat that cannot be burned, leading to oxidative damage. Here is a good review: http://winstonsalempersonaltraining.com/wp-content/uploads/2011/06/Does_Cardio_After_an_Overnight_Fast_Maximize_Fat.3.pdf
Thanks for the link, however I understand that these studies are looking at a different situation to the one I am looking at and the response also depends on the type of exercise too. The intensity of the endurance exercise can impact whether there are problematic side-effects and also will affect how much fat is being burned (and therefore whether there is fat being liberated that can’t be burned).
The studies are looking at genuinely low-carb state where the person has been low carb for some time and their glycogen stores are significantly depleted.
For long-distance walking and cycling, which I am well-adapted to, my muscles are very efficient and don’t usually use much glycogen for the effort (a bit like the effort required for a generally active individual to stroll around the shops) – for a short walk or ride they may even use little enough glycogen that I can replenish it simply through the vegetables I eat with my dinner. However if you do something excessively fatiguing to the muscles (so that you have used a significant amount of the glycogen store in the muscles which was created by the carbs) then it is important to consume something that replenish the stores in due course, and certainly before they run out, ensuring that when they are next needed there is glycogen available.
As an example, when I’m on a walking trip I may be walking for 8-10 hours a day. No matter how efficient I am that will affect my glycogen stores noticeably, although it won’t deplete them completely as my body will use a combination of fat and glycogen for fuel depending on the muscular effort involved. As a result I’m not yet destroying muscle to release the energy in protein or relying solely on fat for fuel (therefore resulting in excessive release of fat). Those trips tend to involve a big pub dinner each day full of potatoes and similar high-carb foods to replenish the stores.
As a result of replenishing glycogen stores through consumption of carbs after any significant effort that uses those stores, it will mean that when you next tax the muscles while you may be perceived to be training in a low-carb state, you actually still have the glycogen stores available in the muscles and liver to provide energy for that effort. In other words you are not genuinely in the low-carb state that these studies refer to (where glycogen in no longer available as an energy source).
The situation of being adapted to burn fat for fuel however is also invaluable as an emergency aid. If glycogen stores become very low the body will try to preserve them as glycogen is the only thing that the brain can use as energy. At that point it will move over to using fat and protein for energy to keep you moving.
Every so often I will run low on glycogen if a route has been more taxing than expected or (as happened last winter) we arrive at our destination and find that there is nowhere to get any food. In those cases I know my body will know how to revert to fat and muscle breakdown to get me to somewhere where I can feed and replenish the stores. Agreed that in those situations there will be side-effects to having pushed yourself past the point of using glycogen stores such as breaking down protein for energy and oxidative damage from excess fat which has been liberated – I’ve certainly had that happen to me and it is an unpleasant feeling. However you would usually avoid this by knowing both your body and what effort you are going to be expecting of it before you will next get an opportunity to consume carbs.
Before adapting I did hit the glycogen-depleted wall a couple of times and was unable to continue walking or cycling. I’ve got strong memories of being sat on the side of a path in the middle of the Cairngorms, about an hour away from our final stopping point where there was some food available, feeling unable to walk, violently sick, light-headed, faint and only managing to walk a few metres at a time. It can actually be very dangerous. In comparison, when we arrived at our destination last winter to find there was no food available I was able to push through for another half hour to somewhere where we could beg a few slices of bread – a good thing considering it was raining hard, dark and the temperatures were low, even if it did have a detrimental impact on my body. As my long-distance running friend points out, he always has sugary drinks provided at feeding stations, so he’s not going to have that happen to him!