FEED-Cystic Fibrosis (FEED-CF)

Inclusion Criteria: 1. Confirmed CF diagnosis 2. Ages 18 years and older 3. Baseline estimated daily total added sugar intake \>16 tsp, as estimated from the Dietary Screener Questionnaire (DSQ). Exclusion Criteria: 1. Nocturnal tube feeds 2. BMI \<18.5 kg/m2 3. Life expectancy \< 12 months 4. Confirmed diagnosis of CFRD 5. Screening OGTT showing fasting hyperglycemia (≥126 mg/dL) 6. Chronic steroid use 7. Current pregnancy or lactation 8. Inability/unwillingness to consume the majority of foods on the menu during the study period 9. MRI-incompatible metal that cannot be removed for testing 10. Uncontrolled exocrine pancreatic insufficiency/malabsorption 11. Clinically instability, defined as no changes in medical regimen (including medications and pulmonary exacerbations) for at least 21 days prior to study visit 12. Initiation of CFTR modulator within previous 8 weeks OR unstable changes in weight and lung function due to CFTR modulator use 13. Actively trying to gain or lose weight 14. Any food allergies or intolerances that cannot be accommodated 15. Any medical condition deemed by the a study physician or PI that may preclude completion of the study or interfere with primary end points.