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Effects of Cystic Fibrosis on Growth and Development

Poor growth in children and trouble keeping weight on during adulthood are one of the most common symptoms of cystic fibrosis (CF). Low weight gain is caused by malabsorption.

What are the causes of poor growth/low weight?

Poor growth and low weight gain tend to occur in people with CF because the thick mucus generated by CF clogs the ducts (tubes) leading in and out of the pancreas, liver, and intestines.


In the pancreas, the mucus created by CF prevents the release of enzymes into the small intestines. These enzymes are needed to break down foods and turn them into usable proteins, fats and carbohydrates. Proteins are needed for growth, tissue repair, and healing. Fats are calorie-rich and full of fat-soluble vitamins that the body needs for growth and to stay healthy. When a body does not process nutrients properly the condition is called malabsorption.

About 80-90% people with cystic fibrosis (CF) have pancreatic insufficiency, which causes malabsorption.1

Calorie intake

In addition to malabsorption, people with CF often burn more calories due to the extra energy it takes to breathe and fight infections. In fact, people with CF need up to twice the daily recommended calories compared to other people of the same age and weight.1-3


All this results in malnutrition, slow growth in childhood, and difficulty gaining weight or keeping weight on throughout adulthood. Other symptoms of malabsorption include greasy, bulky stools, stomachache, and excessive gas.1-4

Diagnosing low weight gain

In infants, a test known as a fecal elastase is used to measure pancreatic function and how well the body is absorbing nutrients.

In babies who were not diagnosed during newborn screening, failure to thrive, trouble gaining weight, malnutrition, and malabsorption may indicate cystic fibrosis if the infant also shows other common symptoms – such as lung infections. These babies are usually given a genetic test to look for CF.

In children and adults with CF, regular BMI (body mass index) charts are used to indicate whether growth, height, and weight are on target.

Treatment for poor growth/low weight

Many techniques and treatments can help a child or adult with CF eat enough to grow or maintain a healthy weight.

Pancreatic enzyme replacements (PERT)

First, pancreatic enzyme replacements (PERT) help the person with CF process their foods more efficiently so they can absorb the nutrients in the food they eat. This allows them to retain more energy from the foods they consume. The amount of enzymes a person with CF takes changes as they age.

Dietary considerations

Next, people with CF are also usually encouraged to eat as much as they’d like of high-calorie, high-fat foods, along with plenty of nutritious fruits and vegetables. People with CF also often need to take extra fat-soluble vitamins A, D, E and K.1-4

Eating fatigue is a common complaint for people with CF. Even if a person with CF feels hungry and eats large amounts of food, it may still not be enough to combat malabsorption.

GI symptoms that may impact growth and development

Other gastrointestinal symptoms that people with cystic fibrosis develop include:

Written by: Jessica Johns Pool | Last reviewed: September 2019
  1. Cystic Fibrosis Foundation. Pancreas. Available at: Accessed 5/8/2019.
  2. Elborn JS. Cystic fibrosis. Lancet 2016; 388:2519-31.
  3. Dennett C. MNT in Cystic Fibrosis Care — What RDs Need to Know. Today's Dietitian. April 2017. Vol. 19, No. 4, p. 44.
  4. Cystic Fibrosis Foundation. Introduction to CF. Available at: Accessed 5/8/2019.