Carbohydrates are converted in your system to glucose and are your main source of energy. Carbs can be broken down into two categories: simple and complex. Simple carbohydrates, like candy, chocolate bars, white bread, commercial muffins and soft drinks, enter your system very fast causing a rapid rise in blood sugars. These elevated levels do not last very long, causing a rapid decrease in energy, focus and performance. Complex carbs on the other hand, are broken down slowly and provide a constant supply of glucose to the blood. Complex carbs allow your energy levels to remain high, allowing you to perform better.