Strength and Muscle Related Outcomes for Nutrition and Lung Function in CF

The goal of the study is to examine multiple markers of anthropometrics, body composition, sarcopenia and frailty and compare them to dual energy X-ray absorptiometry (DXA) output, which is considered the current clinical gold-standard tool to measure body composition. The result of this study will provide detailed data regarding the nutrition and body composition within this Cystic Fibrosis population and also provide a baseline evaluation for use of these biomarkers in the future studies including evaluation of nutritional intervention. Further, the study will also include psychosocial and other patient-reported outcomes and medical contributors to understand their contributions to the nutritional failure in the adult advanced lung disease population. Finally, the study will evaluate both established and emerging nutritional and body composition parameters and link them to clinical outcomes in adults with CF across the spectrum of pulmonary function.

Inclusion Criteria:

* Cohort 1: Participants are eligible if their percentage of predicated forced expiratory volume in 1 second (ppFEV1) is \<70% during the 12 months prior to enrollment (\>50% of measurements, eliminating periods of exacerbation)
* Cohort 2: Participants are eligible if their percentage of predicted forced expiratory volume in 1 second (ppFEV1) is 70% or greater during the 12 months prior to enrollment (\>50% of measurements, eliminating periods of exacerbation).
* Both cohorts match by age, gender, race and CFTR genotype severity.

Exclusion Criteria:

* No prior solid organ transplantation
* No initiation of an investigation drug within 28 days prior to and including Baseline Visit.
* No initiation of new chronic therapy (e.g., ibuprofen, azithromycin, inhaled tobramycin, Cayston, CFTR modulator, etc.) within 28 days prior to and including Baseline visit.
* No acute use of antibiotics (oral, inhaled or IV) or acute use of systemic corticosteroids for respiratory tract symptoms within 14 days prior to and including Baseline visit.
* For the BIA sub-study - Individuals with an implanted pacemaker will be excluded.
* No initiation of a drug for weight loss (such as a GLP-1 receptor agonist) or bariatric surgery within 6-months prior to and including the Baseline visit.
* Patients with continued rapid change or extreme GI symptoms related to weight loss therapy should be excluded at the discretion of the study investigator.