The Effects of Cystic Fibrosis (CF)

CF affects the lungs and the ability to get nutrients from food.

The effect of CF on the lungs

People with CF tend to have thick, sticky mucus in their lungs. This makes it harder for the lungs to clear germs. This can lead to infection, a loss in lung function, and pulmonary exacerbations.


Loss in lung function (FEV1)

FEV1 is forced expiratory volume in 1 second. It is measured using a spirometer. Often, a person's FEV1 is compared with others of a similar age, sex, and height. This can be referred to as percent predicted FEV1 or ppFEV1.

  • On average, lung function (FEV1) for a person with CF declines 1 to 3 percentage points each year
  • Damage to the airways in the lungs may occur before a loss of lung function is even detected with an FEV1 test
  • Younger people with CF generally have greater lung function than older people with CF

Pulmonary exacerbations

Pulmonary exacerbations are periods when CF symptoms get worse and require medical attention. This will include the use of an antibiotic. Pulmonary exacerbations may be the result of infections. During a pulmonary exacerbation, CF respiratory symptoms such as coughing and the amount of mucus in the lungs may increase. A person may also lose weight during a pulmonary exacerbation.

  • Lung function may decline faster in people who have more frequent pulmonary exacerbations
  • The damage pulmonary exacerbations cause to the lungs may be permanent

The effect of CF on nutrition

Most people with CF do not make the enzymes that the body needs to break down food. This makes it hard for their bodies to absorb fat, vitamins, and nutrients from what they eat. As a result, it may be hard to get the calories needed to gain or maintain weight.

One goal of CF treatment is to improve nutrition to help people gain or maintain weight.

A person’s weight and height are used to determine body mass index, or BMI. For people who have reached the age where they stop getting taller, an increasing or stable BMI is likely the result of increasing or stable weight.