People with cystic fibrosis and their caregivers know that the better the patient's nutritional status, the better their survival, lung function, wellbeing, and mental capabilities.1^–3 Poor nutrition is also associated with delayed puberty, a higher risk of pneumothorax, and a worse outcome after lung transplantation.4 5

The increased demand for energy in cystic fibrosis is well recognised.6 Despite this, almost 20% of children with cystic fibrosis fall below the fifth centile for weight set by the Centers for Disease Control and Prevention,7 and their height and weight z scores often decline with age. Combating nutritional failure to ensure normal growth and weight gain …