Can You Run an Expedition on Fat?
Most sports nutritionists maintain that carbohydrates are the body’s primary fuel source. But certain Paleo advocates beg to differ stating you can equally run an expedition on fat. But is this possible? Is it an efficient fuel supply? And by what nutritional mechanisms does this work? Going against the grain of the high protein diet and equally disagreeing with a carb backloading protocol, here sports scientist Ross Edgley explores the science of the high fat diet.
Over to Ross...
Traditional Carbohydrate Wisdom
Firstly let’s examine the traditional school of thought surrounding nutrition and endurance events (applicable to both sport and expeditions). Research published in the European Journal of Applied Physiology and Occupational Physiology theorise that carbohydrates are an athlete’s primary source of fuel. Granted protein shakes and fat-based supplements are not without their merits (but that’s a whole other article). Instead aforementioned research—and most traditional sports scientists—have forever been full of praise for a hearty and simple bowl of porridge. It seems for good reason too.
That’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 six 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 5km" adding, “Furthermore, the men in the carbohydrate group ran the 30km 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."
An idea that also 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’. Basically showing how avoiding carbohydrates pre-workout could directly reduce your muscle building potential in the weights room.
Revolutionary Fat Knowledge
So why is it professional cyclist Dave Zabriskie, ultra-marathon runner Tom Olson, gold medal triathlete Simon Whitfield and even NBA star Lebron James all forgoing the carbohydrates in favour of a high fat diet? Surely this is sporting suicide and anyone who adopts a similar approach on a lengthy expedition is destined for failure?
Well not when you consider Tom 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 lead 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 of running such a long race 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.
So whose dietary protocol would it be wise to follow? Well here we explore the science.
Fat Fuelled vs Carbohydrate Fuelled
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 is a more sustainable fuel source and provides the, “largest energy reserve in the body" that can provide enough energy to last about five days. In contrast muscle glycogen reserves are limited and at most could provide energy to sustain 100 minutes of exercise.
An idea 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 Sherpa 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+ a day trek.
Hence why they chow down on copious amounts of tea butter. Since butter is not surprisingly super high in fat and 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 Sherpas have opted for fat over carbohydrates for hundreds of years.
One final example (and earliest documented demonstrations of physical stamina fuelled by fat) was the arctic Schwatka expedition of 1878-80 where explorers went in search of the lost Royal Navy Franklin Expedition. Sponsored by the New York Herald and the American Geographical Society the team left the west coast of Hudson’s Bay in April of 1879 with a month’s supply of food (mostly walrus blubber) and ammunition for hunting. After covering 3000 miles on foot over ice, snow and tundra they ran out of supplies and continued, hunting and fishing as their only source of food.
The leader of the expedition, Lt Frederick Schwatka, was a graduate of both West Point and Bellevue Hospital Medical College. His summary of the expedition was published as a news article in the New York Herald. The fascinating 117-page book described how he and his team survived and thrived on a high fat Inuit diet once their bodies’ adapted:
“When first thrown wholly upon a diet of reindeer meat, it seems inadequate to properly nourish the system and there is an apparent weakness and inability to perform severe exertive, fatiguing journeys. But this soon passes away in the course of two or three weeks. At first the white man takes to the new diet in too homeopathic a manner, especially if it be raw. However, seal meat which is far more disagreeable with its fishy odor, and bear meat with its strong flavor, seems to have no such temporary debilitating effect upon the economy."
Worth noting is this was years before our current understanding of science and the Paleo craze.
So in summary, should we abandon the conventional bread and pasta and instead boil the kettle for some butter tea? Well not so fast. Research published in the, “Advances in Enzyme Regulation" states that some tissues in the human body actually depend on glucose as their main fuel supply. Specifically the brain which virtually solely uses glucose except during prolonged starvation.
In fact, it consumes about 120 grams per day (420 calories of glucose) and accounts for 60% of the utilization of glucose by the whole body in the resting state. Notably fatty acids do not serve as fuel for the brain, because they are bound to albumin in plasma and so do not traverse the blood-brain barrier. In starvation, ketone bodies generated by the liver partly replace glucose as fuel for the brain.
Fuel and energy for muscle tissue on the other hand can come from glucose, fatty acids and ketone bodies. This is because as fatty acids increase in the blood (due to a higher content in the diet), they are used by skeletal muscles and certain other tissues in preference to glucose. This is achieved through a process known as Beta-Oxidisation and the Kreb Cycle. Essentially where fats are transformed into ATP stores (the body’s molecular form of energy) and when there is enough obtained from fatty acid (or ketone body) oxidation, the rate of glycolysis is decreased. Put simply, when there’s enough fat in the diet carbohydrates are spared.
For this reason (concerning performance and not fat loss which is a whole other article) consider the carbohydrate-fat-dual approach. An idea supported by Rob Wolf (Paleo expert) who recommends, when building an aerobic base, consume 17 to 19 calories and 0.8 grams of protein per pound of body weight every day. Eat 50 to 100 grams of carbs, and consume the rest of your calories from fats.
Notice even someone considered an expert in Paleo, high fat eating doesn’t recommend completely cutting carbohydrates. This is because scientists theorise that sustained exercise at a high power output requires the utilisation of both fat and carbohydrates. It’s called the glucose/fatty acid cycle and it plays an important role in lengthy expeditions. Essentially fatty acids are used as energy which reduces the rate of glucose (carbohydrates) used.
But whilst this carbohydrate-fat-dual approach might be considered optimal in theory, practice might be very different. For this reason it’s always important to consider the fuel sources available (much like Sherpas and Schwatka did) and even when they are available understand how your body personally responds to each to nutrients like Tom Olson.
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