The term applied to an organic substance in which the hydrogen and oxygen are usually in the proportion to form water. Carbohydrates are all, chemically considered, derivatives of simple forms of sugar and are classified as monosaccharides (e.g. glucose), disaccharides (e.g. cane sugar) and polysaccharides (e.g. starch). Many of the cheaper and most important foods are included in this group, which comprises sugars, starches, celluloses and gums. When one of these foods is digested, it is converted into a monosaccharide and absorbed in this form. Excess carbohydrates, not immediately needed by the body, are stored as glycogen in the liver and muscles. In DIABETES MELLITUS, the most marked feature consists of an inability on the part of the tissues to assimilate and utilize the carbohydrate material. Each gram of carbohydrate is capable of furnishing slightly over 4 Calories of energy, with excess long-term intake being a prime cause of OBESITY (See DIET.)