Not Just a Man's World

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.

Related posts:

1. Lessons learned: the benefits of being fat-adapted
2. Lessons learned: exercise and the menstrual cycle
3. Blog-watch: low carb diets
4. Blog-watch: pregnancy diet and exercise