Carbohydrates are the preferred energy source of the brain and nervous system. They provide energy for muscle movement and red blood cells, and they play a role in the regulation of fat metabolism. Fifty-five to 60 percent of a person's daily calories should come from carbohydrates -- in a 2,000-calorie diet, that is approximately 1,100 to 1,200 calories (275 to 300 grams of carbohydrate).
Carbohydrates are composed of smaller units containing carbon, hydrogen, and oxygen, otherwise known as sugars, and are classified as simple or complex. Simple carbohydrates, such as sucrose (table sugar), fructose (fruit sugar), and lactose (the sugar found in milk), are more quickly broken down into glucose and absorbed by the body than complex carbohydrated, found in plant-based foods such as grains, legumes, and vegetables.
The Professional Chef, 7th Edition by The Culinary Institute of America