Patients with CF need to be frequently monitored because nutritional needs change with disease progression and normal growth. To maintain a desirable body weight and prevent or correct nutritional deficiencies, CF patients might have to consume twice as many calories as recommended for healthy children and adults. Increasing the intake of calories can also aid in adequate fat, vitamin, and mineral absorption.
 
Nutritional therapy helps prevent complications, such as glucose intolerance, intestinal obstruction, cirrhosis, and pancreatic disease. Vitamin and mineral supplements such as the fat-soluble vitamins A, D, E, and K are often used. Since these vitamins use dietary fat is necessary for absorption of these vitamins, high-fat food consumption is often encouraged. Fat is also the most concentrated source of calories and improves the palatability of foods, and with caloric needs so high in CF patients, this becomes essential. Protein deficiencies are most likely to occur during periods of growth and infection.

Patients with untreated pancreatic insufficiency commonly have profound malabsorption of bile. Up to 60 percent of adolescents and adults with CF have gallbladder abnormalities. Treatment of pancreatic insufficiency with pancreatic enzymes will decrease bile acid loss, thus decreasing the risk of gall stones. If gall stones are forming, ursodeoxycholic  acid (ursodiol) therapy is used to help dissolve the stones and increase cholesterol production in the liver.