It is known that complex carbohydrates provide more sustained energy over time than simple sugars such as sucrose. complex carbohydrates are polysaccharides, which are long chains of smaller sugar molecules bonded together. simple sugars are monosaccharides that contain only one molecule. why do complex carbohydrates provide more energy over time versus simple carbohydrates? complex carbohydrates have more chemical bonds to break than simple sugars, which takes longer for the body to digest and provides more units of energy for the body to use. complex carbohydrates have bonds that contain more thermal energy than those in simple carbohydrates, which is released when they go through the digestive process. complex carbohydrates provide calories for the body while simple carbohydrates provide calories. calories are bigger than calories and provide more energy. complex carbohydrates take less energy to digest, which means that the body does not spend all of its calories digesting the food. this saves calories for the body to use later.