Fast releasing carbohydrates are called simple carbohydrates. By eating fast released carbohydrates , you increase your blood sugar rapidly and get a quick release of energy. In response, your body makes insulin, which lowers the glucose level. They are fast releasing because you get a burst of energy and the energy lasts only a short time. The best time to eat fast carbs is about 30 minutes before you begin to exercise, and the best snack is one that combines carbs and protein, with an emphasis on the carbs.