Let's take a step back and cover some nutrition basics before we look at the differences between simple and complex carbohydrates. The three calorie-providing components of food are carbohydrates, fats and proteins. Carbohydrates are by far the most abundant of the three. They are found in a very wide variety of foods. For example, oranges, table sugar, potatoes, pies, bread, green peas, honey, biscuits, popcorn, non-fat milk, soda, candy, carrots and grapes are all rich sources of carbohydrates.
Carbohydrate means carbon dioxide combined with water.
Carbs and protein contain four calories per gram, whereas fat contains nine calories per gram. So fats provide more than twice as many calories, gram for gram, as do carbs or protein. Most, but not all, carbohydrates come from plants. Fruits, vegetables, grains and legumes are all of plant origin. The only animal-based carbohydrates are dairy foods.