Ross Edgley is an athlete adventurer, sports scientist and co-founder of The Protein Works. Last year he made history by completing the world's first 'tree-athlon': an Olympic distance triathlon with a 45kg tree trunk strapped to his back to raise money for eco-charities. He also ran a marathon every day in January, and has previously completed a marathon while dragging a Mini. Ross takes a keen interest in fell running - both its athleticism and heritage.
Trail running is brutal. The pace, gradients and sheer duration of each run will test the limits of both your lungs and legs - but what’s often overlooked is the key role that nutrition will play. This is because few runners understand the final time you clock on your GPS watch will be determined long before you lace up your trainers and stare up a sheer vertical mountain ascent. This is because the best runners in the world aren’t just good at running - they’re also good at eating. Whether they know it or not, they are experts in bioenergetics ― the study of the transformation of energy in living organisms ― and they know what to eat, how to eat it and when to eat. Which is why I’ve put pen to paper to explore the intricacies of endurance-based nutrition, starting with the growing trend to fuel your runs on fat.
carbs: tried & tested
For years carbohydrates have been considered our body’s primary fuel source, with a hearty and simple bowl of porridge the best way to start any run. Why? Years of tried and tested research is the short answer. But specifically it’s because researchers from Loughborough University set out to quantify the difference carbohydrate intake made to a runner’s performance. They believed that reducing the carbohydrate content in the diet would have a direct impact on performance. To test this they took 18 runners (12 men and 6 women) and had them complete a 30km time trial. In the first trial the diet of the runners was not modified at all. Then seven days later the runners were randomly assigned into two separate groups. Both groups consumed the same amount of calories, however the diet of one group was predominantly made up of carbohydrates. The other group was lower in carbohydrates and supplemented with fat and a protein powder supplement to compensate for the lower carb content.
Following the experiment scientists stated, “The carbohydrate group ran faster during the last 5 km” adding, “Furthermore, the men in the carbohydrate group ran the 30 km faster after carbohydrate loading.” This lead to the conclusion—and widely held belief—that, “these results confirm that dietary carbohydrate loading improves endurance performance during prolonged running.”
This idea holds true for strength athletes, too. Researchers from the University of Queensland subjected strength athletes to a carbohydrate restricted diet to analyse its effects on performance. After a 2-day carbohydrate restriction program athletes performed three sets of squats with a load of 80% of one repetition maximum. What they found was the carbohydrate restriction program caused a ‘significant reduction in the number of squat repetitions performed’. This showed how avoiding carbohydrates before exercising could directly reduce your muscle-building potential in the weights room.
efficient fat fuel
So why would you ever consider ditching a cupboard full of carbohydrates for a fridge full of fat? Surely that’s sporting suicide? Well, not when you consider Timothy Olson came 6th in the 2011 Western States 100-mile Endurance Run on a high carbohydrates diet when he was plagued with stomach cramps which led to 20 ‘bathroom’ breaks in the latter stages of the race. Now it must be pointed out Olson may have been suffering from a gluten intolerance which caused the cramps, therefore carbohydrates should definitely not be vilified in this situation.
But amazingly this lead him to cut out wheat and most carbohydrates in favour of a high fat diet. When the 2012 Western States 100 rolled around in June 2012, Olson was ready to take on this challenge fuelled mainly by fat. The result? A victory in record time (21 minutes faster than the previous course best) - an outcome that’s been considered revolutionary in sport science circles. But then maybe not so much for Siberian Evenki herders who trek through -30 degrees temperatures for miles on reindeer butter. Or Tibetan Sherpas who are widely considered to be among the fittest endurance adventurers on the planet. Fuelling their travels with various forms of butter tea deemed unpalatable by some - it’s made from tea leaves, water, salt and lots of butter, after all. So whose dietary protocol would it be wise to follow?
Research published in the Current Sports Medicine Reports states, “The number of gruelling events that challenge the limits of human endurance is increasing. Such events are also challenging the limits of current dietary recommendations.” The authors then add that traditionally high carbohydrate diets have been favoured but, “there are some situations for which alternative dietary options are beneficial.”
These circumstances are best described in the nutritional journal entitled, “Human Muscle Fatigue: Physiological Mechanisms.” Researchers from the Department of Biochemistry at the University of Oxford stated that the energy needed to sustain exercise for a long period of time comes from the oxidisation of two fuels, namely glucose and long-chain fatty acids. Interestingly, they state that the latter (from sources like almond butter, cashew butter or pure MCT powder) is a more sustainable fuel source and provides the “largest energy reserve in the body” that can provide enough energy to last about 5 days. In contrast, muscle glycogen reserves (from carbohydrates) are limited and at most could provide energy to sustain 100 minutes of exercise.
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This idea is supported by researchers from the Centre for Human Nutrition at the University of Colorado who stated, “Glycogen storage capacity in man is approximately 15 g/kg body weight.” This means for a small, endurance-gifted runner who weighs 65kg will only be able to store 975g of carbohydrates at the very most. Not very much and certainly not enough for a 30-mile trek into the mountains. Many athletes are turning to fat as a primary fuel source, since fat itself contains 9 calories per gram compared to 4 calories per gram of carbohydrates. So when faced with the decision to choose a calorie/energy dense fuel source that’s easily transportable, is it any wonder more runners have opted for fat over carbohydrates.
So what does this all mean for your next trail run? Basically that modern science it still trying to decide what the best running fuel is. So whilst nutritionists and researchers continue to argue among themselves, the best advice would be to experiment and test everything and anything yourself. Since the relatively new field of research of nutrigenomics ― the field of study concerned with how our genes interact with our nutrition ― it seems for all the studies in the world, you are your best expert and only you will know how you assimilate nutrients based on your own biological identity.
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