Carbohydrates are chemical compounds that typically exist in nature in two forms, carbohydrates are called either simple or complex. The simple carbohydrates are single compounds and the simple carbohydrates when they connect together form the complex carbohydrates.
Carbohydrates are sugars like glucose, fructose and lactose; these are examples of the simple form of carbohydrates. Fruits, milk and milk products, and refined products such as sweets, table sugar and cakes contain the simple forms of carbohydrates (sugars).
Natural examples of the complex carbohydrates are the starch (glycogen) containing vegetables, legumes, rice, pasta, cereals and bread
The energy that results from the body digesting and using these different types of carbohydrates is different between these two forms of carbohydrate. In short, not all carbohydrates yield the same amount of energy. This is because some carbohydrates require more energy to break them down than other carbohydrates do. More energy and time may be spent to utilize the different forms of carbohydrates so the body gets a different ‘return' from some carbohydrate groups. Remember that almost all forms of carbohydrates have to be converted to glucose for the body and the brain to use. The effectiveness or rapidity that the body can use a carbohydrate is important, and a measure of this effectiveness is called the glycemic index.