Purpose of review: Nutritional status impacts on the progression of cystic fibrosis. Current guidelines recommend the use of anthropometric indicators to classify nutritional status and identify malnutrition. However, the current nutrition-classification systems are problematic. I summarize these problems and review recent progress in the development of evidence-based anthropometric criteria for classifying nutritional status in cystic fibrosis patients.
Recent findings: Percentage of ideal body weight as a malnutrition index is flawed. In children with cystic fibrosis, this index underestimates the severity of underweight in short patients and overestimates it in tall patients. In adults with cystic fibrosis, percentage of ideal body weight based on the Metropolitan Life Insurance reference weights for medium/large frames overestimates the severity of underweight. Body-mass-index percentile for children and body mass index for adults as underweight indices have been proven to be valid. Strong associations between body mass index and lung function are also observed, but cutoff values to maintain a desirable level of lung function can vary.
Summary: Body mass index should replace the use of percentage of ideal body weight for classifying underweight in cystic fibrosis patients. More research is needed to identify appropriate indicators to classify short stature in children with cystic fibrosis.