The simple carbohydrates are easy to be digested such as sugar. The complex carbohydrates are not easy to digest. Therefore, complex carbohydrates require more time and energy to first break into simple carbohydrates and then into ATP (adenosine tri phosphate). These ATP molecule provides energy, hence ATP is considered as energy currency. The complex carbohydrate are basically starch and the simple carbohydrates are glucose, fructose, and sucrose etc. Hence, complex carbohydrates release more energy as compared to simple carbohydrates.