This is impaired absorption of nutrients from the GI tract.

Many different conditions and circumstances can affect the ability of the small intestine to absorb nutrients adequately. Examples include a fault in the digestive process, such as a failure to produce enzymes needed to break down certain foods; structural defects or tumors in the intestine itself; inflammatory processes, intestinal infections, and other diseases; and congenital defects.

Injury or surgical removal of portions of the...