The Effect of a Pre-meal Snack and/or Exercise on Post-prandial Glycemic Excursions in Adults With Cystic Fibrosis

The investigators are proposing a randomized pilot study to explore the impact of a soy beverage of carbohydrates and protein early in the morning, to stimulate and initiate secretion of Insulin to reduce PPG excursions of the following a lunch in adult patients with CF. Investigators will also study the impact of a post meal exercise on the PPG excursion. Fourteen participants will be included and will each perform a 4-hour intervention in cross over design according to those 4 following experimental conditions:

• Consumption of 200ml of water (flavored) + breakfast of 90g of carbohydrates (CHO) for men and 80g for women; Sedentary activities throughout the study [condition control]
• Consumption of 200ml of soy beverage + 90g of carbohydrate (CHO) breakfast for men and 80g for women; Sedentary activities throughout the study [snack effect on PPG excursion]
• Consumption of 200ml of water (flavored) + breakfast of 90g of carbohydrates (CHO) for men and 80g for women + physical activity practice (3min walk at 60% VO2max every 30 minutes, x5); [exercise effect on the PPG excursion]
• Consumption of 200ml of soy beverage + breakfast of 90g of carbohydrate (CHO) breakfast for men and 80g for women + physical activity practice (3min walk at 60% VO2max every 30 minutes, x5). [Combined snack and exercise effect on the PPG excursion] Main result: plasma glucose area under the curve. The underlying mechanisms, insulin, incretin hormones (GLP-1 and GIP), acceptability and side effects (mealtime hyperglycaemia) should also be measured. At the end of this pilot project, the investigators will have established a pre-meal snack and/ or postprandial exercise have a positive impact on PPG.

Inclusion criteria

• Diagnosis of cystic fibrosis,
• Be over 18 years old.

Exclusion criteria

• Pharmacological treatment for cystic fibrosis related diabetes.
• Signs of secondary infection: the test will be practiced at least 1 month after the end of infection treatment
• People with severe gastrointestinal illness (Crohn's disease, celiac disease and a recent history (<1 year) of bowel obstruction).
• Allergy to one of the ingredients of the menu (example: celiac disease)
• According to the judgment of the investigator, medications or conditions that could interfere with glucose metabolism (eg: oral steroids)
• Pregnancy in progress
• Corrector or potentiator prescribed whose dose is not stable the last 2 months.