Cystic fibrosis does not cause severe weight gain but rather often causes weight loss, delayed growth and problems maintaining a healthy weight, according to MedlinePlus. Cystic fibrosis is a genetic disease that creates a thick mucus that obstructs tubes, ducts and passageways in the body, reports Mayo Clinic.
The thick mucus associated with cystic fibrosis also obstructs digestive enzymes traveling from the pancreas to the small intestine, inhibiting the absorption of nutrients, states Mayo Clinic. The lack of nutrients within the body then affects growth and weight gain, making it difficult for cystic fibrosis patients to retain weight.
In addition to poor weight gain, cystic fibrosis can also produce coughing, wheezing, constant chest infections and greasy stools, adds Mayo Clinic. Those with cystic fibrosis are also more likely to experience other illnesses caused by the build up of mucus, specifically in the respiratory, digestive and reproductive systems. These illnesses can include brochiesctasis, diabetes, hemoptysis and respiratory failure.
Although cystic fibrosis cannot be prevented nor cured, most children with cystic fibrosis do well until they reach adulthood, which is when lung disease worsens, according to MedlinePlus. On average, those with cystic fibrosis live until 37 years of age, as of 2015. Most die from complications associated with lung problems.