FEED-Cystic Fibrosis (FEED-CF)

This study (FEED-CF) investigates whether reducing added sugar intake in adults with cystic fibrosis (CF) can improve how the body processes sugar and reduce the risk of developing cystic fibrosis-related diabetes (CFRD) — a complication that affects about 50% of adults with CF and significantly worsens their lung function and overall health. People with CF often consume high amounts of sugar to meet their elevated caloric needs, but this may contribute to impaired insulin function. Adults 18 and older with confirmed CF who consume more than 16 teaspoons of added sugar per day (assessed by a dietary screener) are eligible. Participants must have a BMI of at least 18.5 and a life expectancy of more than 12 months. Those already diagnosed with CFRD, with fasting blood sugar above 126 mg/dL, on nocturnal tube feeds, currently pregnant or breastfeeding, or who have started a CFTR modulator drug within the past 8 weeks are excluded. Cystic fibrosis-related diabetes dramatically worsens outcomes in people with CF, yet preventing it has received little research attention. A dietary intervention that could delay or prevent CFRD would be transformative — not only improving metabolic health but potentially also lung function. This trial addresses a genuinely neglected but very important question in CF care.