One of the most talked about facets of nutrition for athletes is the timing of carbohydrates for performance in endurance. There are a lot of studies out there with varying results. One frustration people have with studies in general is how rigid they are in design. While studies typically need to be well controlled in order to be useful for application to sport, it can be easy to throw your hands up in the air and say, “That information is all well and good, but I don’t ever exercise in such strict conditions.” Wouldn’t it be refreshing, at least sometimes, to look at studies that were more like real life?
A review in the Nutrition Journal thought it would be nice to see how carbohydrates affected athletes who exercise in normal conditions. What’s the difference between real life conditions and study conditions for the reviewers?
The first difference was what nutritional state the athletes were in when being studied. Most studies look at athletes in a fasted state, and for good reason. There’s limited use seeing how x grams of carbs impacts performance when one person might have eaten 100 grams of carbs just before getting to the lab and another person in the same study might not have eaten since the day before. That said, knowing how your body reacts to carbs taken in at a specific time in a more normal state is important. The other difference is the type of exercise. In most studies, researchers look at how long it takes for an athlete to become exhausted. However, in real life situations we exercise more often for time or distance.
Consuming carbs to boost performance in endurance training is a very common practice, and many studies agree on this. However in this review when removing stringent conditions the researchers found that the waters were muddied. In bouts of exercise less than 70 minutes, there was no observed benefit to carb loading or consuming carbohydrates during exercise. In bouts of longer than 70 minutes, a little over half of the studies reviewed indicated a benefit to consuming carbs in a loading manner or during exercise itself. Less than convincing, in my opinion.
The results could be due to the fact carbohydrate intake benefits people in a fasted state more than those not in a fasted state. So for those of us who eat normally, focusing the timing of your carb ingestion might not be critical to your performance. It should also be noted that none of the athletes in any of the studies reviewed were elite. However, my intuition says that an elite athlete would obtain an even more reduced benefit from specialized carb consumption due to a greater ability to metabolize fats for fuel.
While maintaining glycogen stores is critical to an athlete’s success, the timing of consuming carbs seems much less important. If you have strong fat oxidation enzyme levels, your ability to maintain glycogen stores is even better than the average person and carb timing probably becomes even less important.
1. Paolo Colombani, et. al., “Carbohydrates and exercise performance in non-fasted athletes: A systematic review of studies mimicking real-life,” Nutrition Journal 2013, 12:16
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