Calling all marathon runners, long distance swimmers and other endurance athletes! For a long time, high carbohydrate consumption and blanket recommendations have been part of endurance sports nutrition practice. However, recent research has shown we need to think more carefully about the way we prescribe carbohydrates to endurance athletes.
We’ve all heard of carb loading- filling up on pasta and bread before a big race or competition. Carb loading and other standard carbohydrate recommendations are centred around providing adequate fuel for training. The purpose of carbohydrate loading, before training or competition, is to increase muscle glycogen stores, which, fuel exercise. Glycogen, however, is a fleeting source and once it runs out, we ‘hit the wall’. This is when the body is forced to switch from primarily carbohydrate fuel to an increased reliance on fat. Hitting the wall is associated with fatigue. Carb loading is designed to delay this fatigue and improve performance.
While loading is a valid carbohydrate protocol, perhaps there are smarter ways to ingest carbohydrate.
Exciting recent studies have found that exercise bouts commenced with low muscle glycogen elicit increased adaptation to exercise. This means that a high fat-low carbohydrate diet, during which glycogen stores are largely depleted, could be beneficial. Contradicting the previous belief, that carb loading is the best way to improve your athlete!
How does it work? No matter how much carbohydrate we consume, glycogen is always a limited store. Hitting the wall is a persistent issue for endurance and ultra-endurance athletes, even if the most extreme carbohydrate load protocols have been followed. Why not instead of delaying hitting the wall (aim for carb loading), we try smash through it?
Unlike carbohydrate, fat stores are abundant in our body. Therefore, they make a great fuel for endurance athletes, as running out will never be an issue. However, using fat as the primary fuel poses a different issue. The body isn’t very efficient at converting fat to energy. This is the reason why hitting the wall is associated with fatigue.
By forcing the use of fat as a fuel, through a low carbohydrate dietary intervention (training specific), it is possible to train the body to more efficiently utilise fat. Therefore, hitting the wall, is not longer such a big deal, and is not associated with as serious fatigue.
Despite being a good idea in theory and research consistently proving in creased fat oxidation efficiency, high fat diets, unfortunately, have not always translated to performance improvements. This is thought to be for a couple of reasons. Firstly, fat is a used to fuel low to medium intensity exercise exclusively. This is fine for the majority of an endurance event where such intensities are relevant, but, what about the break away? What about times where a short high intensity sprint is necessary to get across the line? Reliance on fat will just not get you there. The inability to operate at ‘top gear’ when consuming a low carbohydrate diet is sometimes deleterious to performance. Furthermore, inability to operate at top gear may reduce vital whole body adaptations to exercise.
A low carbohydrate diet is neither easy, practical nor sustainable. In order to achieve the adaptions that make a low carbohydrate diet effective, fat must be the main macronutrient consumed. This is extremely hard to achieve. Meals need to be 80% fat, significantly limiting dietary choices. Not to mention, it’s an all or nothing diet. This means that you can’t be good all week and celebrate with a slice of bread on the weekend (wild!). For this reason, training smart is recommended to only the most dedicated athletes.
Another issue with ‘training smart’ is that each athlete is highly individual and some will respond well to the diet, while others will not. For this reason, it is recommended you test your response to the diet prior to important competitions. In fact, some more recent studies have even shown performance decrement with low carbohydrate, high fat diets.
By training specific, the pros and cons of training hard and smart are address. It is the attempt to find a middle ground. This might include training low every second day. Or training low for a brief period before training hard immediately prior competition. By doing this, the athlete is likely to reap at least some benefit from each dietary approach.
Training specific also means monitoring the athlete’s individual response to carbohydrate protocols, and adjusting intake accordingly.
For this reason, training specific is most highly recommended for endurance athletes.
Where to from now?
Carbohydrates and endurance athletes is a very exciting and forever evolving field. Therefore, it can be hard to keep up with the research.
Navigating this field can be tricky and athletes are often left feeling lost and without direction. Currently, the best protocol is to continue carbohydrate loading practices for 2-3 days prior to competition. Effective carbohydrate loading requires consumptions as high as 6-12 g/kg. However, this is highly individual and many athletes find the gastro-intestinal discomfort too great at 12g/kg, but experience performance decrement at 6g/kg. It’s all about finding what is optimal for the individual.