Children with cystic fibrosis require increased caloric intake to maintain appropriate growth, an important determinant of long-term outcomes. This study seeks to determine the feasibility of using a novel therapeutic food to promote weight gain and growth in children with cystic fibrosis.

Inclusion Criteria:

• Cystic Fibrosis diagnosed by sweat test or genetic testing.
• Exocrine Pancreatic Insufficiency and receiving pancreatic enzyme replacement therapy
• BMI or weight for age of less than the 50th percentile

Exclusion Criteria:

• Cystic fibrosis related diabetes mellitus
• Cystic fibrosis related liver disease.
• Anaphylactic or other allergy to peanut, cow's milk, oat flour or other RUTF ingredients.
• Patients who are status-post lung or liver transplantation
• Currently receiving enteral supplemental nutrition through gastrostomy or nasogastric tube.