Carbo-Loading – Separating Fact from Fiction!

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Nutrition has undeniably been an integral part of performance in the field of sports, training and athletics. We've come a long way in terms of identifying peak performance foods and supplements that help us perform and train better. Endurance sports is one popular subculture. It is also a category for which a plethora of research related to nutrition has been done. Which food to eat? What should be the timing of the food intake? What should be the macro-nutritional breakdown? Which micro-nutrients are important for performance? These questions are a few of the basic ones that nutritionists and dieticians try to answer.

Like every other field of sports, endurance sports has been plagued by many myths and misinformation, 'Carbohydrate loading' being a prime example. The myth goes:

'Carbo-Loading is essential for performance enhancement in endurance sports such as marathon running, triathlons, long distance swimming and cycling.'

What is Carbo-Loading?

The basic theory behind carbohydrate loading is that, Glycogen reserves (simple sugars used by our body as the primary source of fuel) are very important for the body during an endurance event and these reserves can be maxed out through rigorous intake of carbohydrates prior to the event. Carbohydrate is the main fuel used by the body during an endurance event. Usually when the Glycogen reserves in an athlete's system drop below a certain level, the athlete then becomes hypoglycemic. This is an indicator of the fact that the blood doesn't contain a sufficient amount of simple sugars. The body then gives more preference to the stored fat as energy fuel.

Marathon Runner

Fat is not a very efficient source of energy and hypoglycemia is one of the major causes athletes 'hit the wall' right in the middle of an endurance event. Carbo-loading is thought to avoid this switch over to fat-burn and it is thought that if we force-feed our body with enough carbohydrates, it will increase its Glycogen reserves, in turn, improving final day event performance and physical output. There are 3 school of thoughts related to Carbo-loading. The old school method of Carbo-Loading as introduced by Ahlborg (developer of this protocol) involved a seven day preparation period prior to race day.

In the first three days of this seven day period, Glycogen reserves are depleted completely through vigorous training and an extremely low-carb diet. Once the glycogen reserves are completely depleted, the body is then fed high carbs for the rest of the three days while light-intensity exercise is pursued. The body is thought to 'over-compensate' for low Glycogen levels by absorbing a greater quantity of Glycogen. This is what is 'thought to happen'. The second method of carbo-loading involves no depletion phase. Athletes are required to eat a well balanced diet in the first three days of the final week. They, then switch to a high-carb diet (70% in proportion) for the last three days leading to the final event.

Debunking The Myth

In theory, the notion of carbo-loading may seem pragmatic but recent studies have shown that this isn't the case. The foremost aim of carbo-loading is to counter hypoglycemic fatigue which has been explained earlier. This means that carbo-loading aims at providing Glycogen for the entire event (whatever applicable sports that might be) or to say the least, delay the onset of hypoglycemic fatigue. But the fact of the matter is that the human body can store approximately as much as 500 g of glycogen in total (liver and muscles). This means that hypoglycemic fatigue is inevitable!

Let's take Marathon running as an example of an endurance event. Marathons typically last for about 3 - 4 hours. Usually, athletes are running at their 60 - 80% of their VO2 max, meaning that they are burning anything around 1000 calories per hour. 70% of these calories come from the stored glycogen (as long as it is available) and the rest comes from fat metabolism. At the end of a marathon, the typical runner burns about 4000 - 5000 calories. Now, coming back to our limited glycogen reserve of 500 g, we see that it accounts for only 2000 calories (1 gram = 4 calories). This means that the rest of the energy expended has to come from metabolism of lipids (fat). Even with extreme forms of Carbo-loading i.e. the Ahlborg method, you can increase your Glycogen reserves by 10 – 15%.

This still isn't enough to avoid fat metabolism and the downside of this method is far greater than the 10% additional glycogen storage space it provides. Restricted carb diet at first can leave you irritable, listless and there can be many digestive complications that can follow due to the initial high protein and fat diet. Another downside is the intense training the athlete must go through to deplete his/her glycogen reserves initially. This can seriously hamper your final day performance rather than improving it. The high carb diet that continues for the last three days can cause bloating and water weight retention. All of these factors are highly undesirable for an endurance event.

What is more beneficial?

New research has pointed out that a well-balanced diet is what is required during the week leading up to the final event day. A day before the event, a high carb diet is a good idea but 'loading' on carbs isn't. What is more important for such endurance events is the nutritional intake during the race. Any form of physical exercise that lasts over 90 minutes is bound to deplete your glycogen reserves. To counter this, simple sugars taken during the race can be much more beneficial than extensive carbo-loading which usually starts a week before the race.

During an endurance event such as the marathon, the runner/athlete should aim at consuming roughly 60 grams per hour of physical exertion (estimated on blood glucose saturations at 70% VO2 max for an average athlete). This can vary according to your body composition and level of exertion. Energy gels, sports drinks are a great source of simple sugars during the race - anything that provides you with enough carbo-replenishment without exerting too much on your GI tract. This can readily enhance your physical performance during the race and is a much better alternative than old-school carbo-loading.

About the Author:

Gohar Khan is a fitness and nutrition expert specializing in the fields of weight loss and endurance training. His expert opinions can also be found at the following website which deals with the dilemma of  how to lose love handles and how to lose weight!

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