One gram of soluble fiber contains about four calories, but insoluble fiber has no calories. Fiber is the part of food that is not broken down during digestion.
Fiber is composed of a chemical bond of sugar molecules that the body has a hard time breaking down. Whole-grain products, such as wheat bran cereal, vegetables and fruit contain insoluble fiber. Fiber is important for stool formation and helps waste move quickly through the colon.
Soluble fiber is found in peas, beans, rice and many other fruits and vegetables. It slows the digestion of carbohydrates and can help regulate blood sugar. A food providing at least 20 percent of the recommended daily value is considered high in fiber, while foods providing 5 percent or less are considered low in fiber.