The Importance of Glycogen

Think of glycogen as the “wick” in a candle and our fat stores as the “wax”. If we have no glycogen, we cannot sustain a flame and therefore cannot burn energy even with lots of stored fat available. Similar to a candle, our body stores of glycogen (the wick) are very small in comparison to fat stores (the wax), but so very essential. In other words, we cannot burn fat without the presence of at least small amounts of glycogen. Therefore, glycogen has to be present for aerobic exercise to continue.

However, glycogen is not only a fuel source for muscles, but also the food source for our brain. Although the muscle can store glucose and burn fat, the brain does neither, but rather feeds on glucose, supplied to it from the blood stream. Since the brain has no fuel storage capacity, it is extremely sensitive to fluctuating glucose levels in the blood. It is well known that depleted blood glucose causes athletes to “hit the wall”, or to “bonk” or “crash”, as athletes with low blood sugar tend to perform poorly because the under-fueled brain limits muscular function and mental drive.