Much has been made in the last 30 years or so about low carbohydrate diets. The basic idea of these types of diets, such as the Atkins diet, is to cause the body to switch from using glucose as an energy source and condition it to use stored fat as the primary source of energy.
Using fat as the primary energy source may be a good way to lose weight, but does a low carbohydrate diet negatively impact running performance? The answer is most likely yes. The reason that low carb diets are not good for serious runners is based on the way muscles produce energy.
During running, muscles produce energy through the breakdown of “glucose” into the high energy molecule ATP. Glucose is a carbohydrate that is found in food sources such as bread, cereals, pasta, etc.- foods that are a big no-no in the low carb diet plans. While the body can use fat as energy when running, glucose is much easier and more efficient for the body to break down. A good illustration of these different sources of energy is seen when a runner competes in a marathon.
Generally, a runner has enough glucose stores in his or her body to run about 2 hours. Once the glucose in the body has been depleted, the body shifts to solely burning fat stores for energy – and the runner “hits the wall.” Any marathoner that has experienced hitting the wall in the later part of a marathon knows the feeling well of fatigue- fat simply is not an ideal source of running energy.
Therefore, in order to get the most out of your training, be careful not to starve your body of the most efficient energy source for your running muscles – glucose – which is supplied in the form of carbohydrates.