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.