Role of Body Fat Distribution in Metabolic and Pulmonary Decline in Cystic Fibrosis (ORBIT-CF)

Inclusion Criteria: CF inclusion criteria 1. confirmed CF diagnosis based on sweat testing by pilocarpine iontophoresis and/or CFTR genotyping with two disease causing mutations 2. be aged ≥ 16 yrs 3. clinically stable, defined as no changes in medical regimen (including medications) for at least 21 days prior to study visit 4. participation in the CFF Patient Registry Longitudinal study inclusion: CF participants who have normal glucose tolerance results after their initial study oral glucose tolerance test (OGTT). Healthy controls inclusion criteria: 1. male or female ages 16 years and older 2. clinically stable. Healthy controls will be recruited who are similar in age, gender, and BMI as the participants with CF. Exclusion Criteria: CF exclusion criteria: 1. diagnosis of CF-related diabetes (CFRD) 2. nocturnal tube feeds 3. life expectancy \<6 months 4. history of or on waiting list for lung transplant 5. un-removable metal that is incompatible with MRI 6. inability or unwillingness to perform major study activities (OGTT, DEXA, MRI) due to claustrophobia, fear of blood draw, or other reasons 7. current pregnancy or lactation 8. study visit falls between window of 1 week to 8 weeks of initiation of CFTR modulator 9. use of chronic oral corticosteroids, 10. in the opinion of the CF Care Team or study physician, participant should not participate in the study, or 11. inability to provide informed consent or assent. Healthy controls exclusion criteria: 1. malignant neoplasm (other than localized basal cell cancer of the skin) during the previous 5 years 2. respiratory (including asthma), endocrine (including diabetes), autoimmune, or other chronic disease 3. HIV or other chronic infection 4. current use of any medications to treat an acute or chronic disease or illness (anti-depressants, anti-anxiety medications are acceptable), 5. acute illness within the past 3 weeks 6. intravenous or oral antibiotics or use of systemic corticosteroids within the past 3 weeks 7. inability or unwillingness to perform major study activities due to claustrophobia, fear of blood draw, or other reasons 8. current pregnancy or lactation, or 9. inability to provide informed consent or assent.