A carbohydrate characterised by chemical complexity and multiple-side chains of glycogen and fibre; complex-carbohydrate-rich foods include whole grains, brown bread, brown rice, vegetables and beans.a compound of carbon, hydrogen and oxygen, the latter two usually in the proportions of water (CH 2 O) n.They are classified into mono-, di-, tri-, poly-and heterosaccharides. Carbohydrates in food are an important and immediate source of energy for the body; 1 gram of carbohydrate yields 3.75 calories (16 kilojoules).arbohydrates may be stored in the body as glycogen for future use. If they are eaten in excessive amounts they are converted to and stored as fat. Rapid ingestion of very large amounts in ruminants and horses causes carbohydrate engorgement. complex carbohydrate.