Carbohydrates, commonly called sugars, are an essential source of energy for the body. They are supplied in the diet through the breaking down of food into nutrients absorbed by the digestive enzymes
in the intestine. They can be used directly by the body or can be stored as glycogen
in the muscles
and thus be rapidly mobilized reserves. Carbohydrates are divided into two groups: simple carbohydrates or monosaccharides, such as glucose, fructose, and sucrose, found in fruits, for example, and complex carbohydrates, assemblies of several simple carbohydrates such as starch
, and cellulose.