A Pilot Study of a Low Glycemic Load Diet in Adults With Cystic Fibrosis

Not Applicable

Completed

• Conditions: Cystic Fibrosis; Cystic Fibrosis-related Diabetes; Cystic Fibrosis With Intestinal Manifestations
• Interventions: Behavioral: Low Glycemic Load Diet

• Registration Number: NCT04519853
• Lead Sponsor: Boston Children's Hospital

Brief Summary

This pilot study will evaluate the safety and tolerability of a low glycemic load dietary intervention in adult patients with cystic fibrosis (CF) in a rigorous feeding study. Specific emphasis will be placed on changes in weight, body composition, and glycemic measures obtained via continuous glucose monitor (CGM) usage.

Detailed Description

Non-pulmonary complications of cystic fibrosis (CF) are becoming increasingly prevalent with the changing landscape of CF care. CF related diabetes mellitus (CFRD) and CF related gastrointestinal (GI) complications have significant effects on morbidity and mortality. Treatment options are limited to insulin therapy for CFRD and symptom control for most GI complications.

BMI is a well-established marker of morbidity and mortality in patients with CF. Many patients consume a high carbohydrate intake to meet their increase caloric needs, potentially leading to complications including post-prandial hyperglycemia, increased inflammation, and abnormal GI motility. Dietary recommendations for children and adults with CF are limited and based entirely on consensus and expert opinion. As patients with CF live longer with highly effective modulator therapy, it is important to understand the effects of dietary composition on short and long-term endocrine, GI, and pulmonary outcomes.

The investigators will conduct a prospective, open-label pilot study in adults with CF and impaired glucose tolerance or indeterminate glycemia to establish the safety and tolerability of a low glycemic load (LGL) diet. Subjects will initially follow their standard diet for a 2-week run-in period, then transition to a LGL diet provided by a food delivery service for the remaining 8 weeks. The investigators will also investigate potential short-term outcomes of dietary carbohydrate manipulation, including glycemic variability measured by continuous glucose monitor (CGM), body composition via DXA, GI symptoms, and quality of life measures.

The investigators hypothesize that a diet lower in carbohydrate content will be safe, tolerable, and associated with weight maintenance or gain, and that a LGL diet will result in decreased glycemic variability via CGM, improved GI symptoms, increased lean to fat mass ratio, and improved quality of life measures over an 8-week period.

Study Timeline

• Study First Submitted: 2020-07-07
• Study First Submitted QC: 2020-08-17
• Study First Posted: 2020-08-20
• Study Start: 2021-10-25
• Primary Completion: 2023-07-01
• Study Completion: 2023-07-01
• Status Verified: 2023-08
• Last Update Submitted: 2023-08-09
• Last Update Posted: 2023-08-14

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 11

Inclusion Criteria

1. Diagnosis of CF
2. Diagnosis of pancreatic insufficiency, requiring pancreatic enzyme replacement
3. Oral glucose tolerance test within the past three years showing impaired glucose tolerance (2-hour glucose ≥140 mg/dL) or indeterminate glycemia (1-hour glucose ≥200), HbA1c 5.7-6.4% in the past one year, and/or or documented random glucose ≥200 in the past one year
4. BMI 21-25 kg/m2
5. 18 years and above

Exclusion Criteria

1. Current use of insulin
2. Most recent HbA1c ≥6.5%
3. History of solid organ transplant or currently listed for solid organ transplant
4. FEV1 <50% predicted on most recent pulmonary function testing
5. Currently receiving enteral nutrition support
6. Current or anticipated pregnancy in the next 1 year
7. Hospitalization for CF exacerbation within 1 month of enrollment
8. Started or stopped treatment with Trikafta or other CFTR modulator within 3 months of enrollment
9. Currently adhering to a low glycemic index or other carbohydrate restricted diet

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Low Glycemic Load Diet	Low Glycemic Load Diet	Feeding study with dietary composition (approximately) 50% fat, 30% carbohydrate, 20% protein.

Primary Outcome Measures

Name	Time	Method
Change in percent time <54 mg/dL	Baseline and 10 weeks	Continuous glucose monitoring
Change in weight from baseline and 10 weeks	Baseline and 10 weeks	Anthropometric measure
Patient reported tolerability of dietary intervention, Likert scale	Single measurement at 10 weeks after diet completion	Single Likert scale question of overall diet tolerability, ranging from 1 (intolerable) to 10 (completely tolerable)

Secondary Outcome Measures

Name	Time	Method
Change in percent time >140 mg/dL	Baseline to 10 weeks	Continuous glucose monitoring
Change in percent time 70-180 mg/dL on CGM	Baseline to 10 weeks	Continuous glucose monitoring
Change in percent time greater than >250 mg/dL on CGM	Baseline to 10 weeks	Continuous glucose monitoring
Change in Patient Assessment of Constipation (PAC) questionnaire score	Baseline and 10 weeks	Likert scale questionnaire with 12 items, each item scored 0-4, total score ranging from 0-48 with higher scores related to worse outcomes
Change in percent time greater than 180 mg/dL on CGM	Baseline to 10 weeks	Continuous glucose monitoring
Change in lean and fat mass	Baseline and 10 weeks	DXA body composition measures
Change in erythrocyte sedimentation rate (ESR)	Baseline and 10 weeks	Laboratory test, measured in mm/hr
Change in percent time less than 70 mg/dL on CGM	Baseline to 10 weeks	Continuous glucose monitoring
Change in CGM coefficient of variation (CV)	Baseline to 10 weeks	Continuous glucose monitoring
Change in percent time less than 50 mg/dL on CGM	Baseline to 10 weeks	Continuous glucose monitoring
Change in Modified Activity Questionnaire (MAQ) score	Baseline and 10 weeks	Questionnaire, units of total hours of exercise over past 12 months, no min or max scores, higher value related to better outcome
Change in intestinal fatty acid binding protein (I-FABP)	Baseline and 10 weeks	Laboratory test, measured in ng/mL
Change in CGM average glucose	Baseline to 10 weeks	Continuous glucose monitoring
Change in CGM glucose management indicator (GMI)	Baseline to 10 weeks	Continuous glucose monitoring
Change in CGM standard deviation (SD)	Baseline to 10 weeks	Continuous glucose monitoring
Number of episodes of symptomatic hypoglycemia	Baseline and 10 weeks	Survey
Change in Patient Assessment of Gastrointestinal Symptom (PAGI-SYM) questionnaire score	Baseline and 10 weeks	Likert scale questionnaire with 20 items, each item scored 0-5, total score ranging from 0-100 with higher scores related to worse outcomes
Change in Cystic Fibrosis Questionnaire Revised (CFQ-R) score	Baseline and 10 weeks	Likert scale questionnaire, 50 items, each scored 0-4, total score ranging from 0-100 with higher value reflecting better outcome
Change in c-reactive protein (CRP)	Baseline and 10 weeks	Laboratory test, measured in mg/L

Trial Locations

Locations (1)

Boston Children's Hospital; 🇺🇸 Boston, Massachusetts, United States