Target BMI Among Patients with Cystic Fibrosis to be Reconsidered According to New Study

March 15, 2022
Giuliana Grossi

More studies need to be done examining the associations of increased weight and outcomes among patients with cystic fibrosis.

New research indicated that the target body mass index (BMI) of a patient with cystic fibrosis (CF) should be reconsidered. While the prevalence of overweight and obesity among patients with cystic fibrosis has been on the rise, it’s unclear whether there’s any benefit associated with increasing weight compared with the normal reference range.

According to the results of a new study, patients with cystic fibrosis who had a normal weight compared with those who were overweight or obese were associated with a higher forced expiratory volume in the first second of expiration. Also, those at a normal weight were at higher odds for cystic fibrosis-related diabetes (CFRD) and pancreatic insufficiency (PI).

The team of investigators, led by Rita Nagy, MD, Institute for Translational Medicine, Szentagothai Centre, Medical School University of Pecs, called for more studies with long-term follow-up to assess the possible adverse effects of higher BMI or higher fat mass in patients with cystic fibrosis.

The Motivation

In the study, the investigators noted that the fatal inherited disease is caused by recessive genetic variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene affecting 1 in 3300 White newborns. This disease affects multiple organs including the lungs, gastrointestinal system, and reproductive system.

Airway infections, chronic inflammation, exocrine pancreatic insufficiency, and complications like CF-related diabetes and CF-related liver disease, are frequent which results in poor quality of life for these individuals.

The European Society for Clinical Nutrition and Metabolism, the European Cystic Fibrosis Society, along with a number of other official organizations recognize the adult and pediatric dietary guideline that focuses on nutritional failure with no recommendation on the management of individuals who are overweight or obese.

In the past 2 decades, overweight and obesity among adults with cystic fibrosis is experienced in 31.4% of individuals in this population, which has more than doubled. However, investigators pointed out that the currently recommended high-fat and high-carbohydrate diet in those with CF could have various effects on the body and even clinical outcomes.

“To fulfill the knowledge gap,” investigators explained, “we aimed to evaluate the differences in clinically significant outcomes, such as lung function, PI, and CFRD, in patients with CF having altered BMI and/or body composition by conducting a systematic review and meta-analysis of the literature.”

The Study

Investigators aimed to evaluate the association of altered BMI or body composition and clinical outcomes in patients with cystic fibrosis. A couple of authors extracted data and had it validated by a third author.

The systematic review and meta-analysis search of 3 databases was conducted in November 2020: MEDLINE (via PubMed), Embase, and Cochrane Central Register of Controlled Trials. Patients above the age of 2 years who were diagnosed with cystic fibrosis and altered body composition or BMI were compared with patients who had the measured parameters within the reference ranges.

The main outcomes were pulmonary function, exocrine pancreatic insufficiency, and CF-related diabetes. The odds ratios or weighted mean differences with 95% confidence intervals were calculated and the hypothesis was formulated before data collection.

The Results

Only 61 records of the 10,524 that were identified, met the criteria and were included in the analysis. From there, 17 studies were included in the quantitative synthesis. The systematic review and meta-analysis included 9114 patients.

Those who were overweight or obese were associated with higher forced expiratory volume in the first second of expiration compared with those at a normal weight. High heterogeneity was shown in the analysis of pulmonary function.

The results show that nutritional status does have an impact on maintaining organ function in patients with cystic fibrosis. According to investigators, a nutritional strategy that increases the BMI closer to the upper limit of the normal BMI is reached should be included in daily protocol.

Further research examining long-term follow-up of higher BMI, body composition, and high-fat diet, is necessary to focus any possible harmful effects of these higher levels. According to investigators, the research suggests that careful evaluation of body composition is needed to be incorporated into everyday clinical practice.

“Our findings suggest that nutritional status plays an important role in maintaining organ function in patients with CF,” investigators wrote. “Because we noted that a higher BMI is associated with better clinical parameters, we advise clinicians to reconsider increasing the currently recommended target BMI (22 for women and 23 for men).”


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