To determine and compare the time-to-hypoglycaemia (defined as plasma glucose <3.9mmol/L) in individuals with type 1 diabetes treated with ultra-Long acting insulin degludec during aerobic exercise with or without prior ingestion of a single oral fructose load.

Glycaemic control remains complex and demanding during exercise for type 1 diabetes (T1D) patients. Traditional treatment guidelines for exercise emphasizing the reduction of insulin doses and/or ingestion of additional carbohydrates are of limited applicability for patients treated with ultra-long acting basal insulin analogues. Dose reductions may require two to three days for modern basal insulin analogues in order to achieve an adapted steady state, hereby increasing the risk of inadequate insulin-following exercise. If T1D patients engage in recreational exercise - as recommended by every international treatment guideline - current treatment strategies may simply not be sufficient.

As a consequence for patients treated with modern basal insulin analogues, it seems more adequate not to modify insulin doses but to apply alternative strategies for recreational exercise. The ingestion of fructose, an insulin-independent carbohydrate, which increases lipid oxidation but attenuates the dependency on carbohydrates may offer a novel strategy. Up to date, only preliminary data for fructose have been produced regarding clinical effectiveness and underlying mechanisms in the prevention of hypoglycaemia. The present comprehensive study aims to investigate the clinical efficacy, feasibility, and safety of a pre-exercise oral fructose load without modification of insulin degludec in T1D patients.

Inclusion Criteria:

• Type 1 diabetes as defined by the World Health Organization (WHO) for at least 1 year or confirmed negative C-peptide (<100pmol/l with concomitant blood glucose >4 mmol/l)
• Male subjects aged between 18-45 years
• HbA1c <8.0% (64mmol/mol) based on analysis from the central laboratory unit of the University Hospital Bern.
• Basal/Bolus-insulin regimen with insulin degludec for at least 3 months, with good knowledge of insulin self-management
• Regular physical activity (at least 30 min of moderate exercise 3 times weekly)
• Written informed consent

Exclusion Criteria:

• Relevant diabetic complications as judged by the investigator
• Total daily insulin dose >2 IU/kg/day
• Hypoglycaemia unawareness (Gold score > 4) or any episode of severe hypoglycaemia as defined by the American Diabetes Association within the last 6 months
• Physical or psychological disease likely to interfere with the normal conduct of the study and interpretation of the study results as judged by the investigator
• Current treatment with drugs known to interfere with metabolism, e.g. systemic corticosteroids, statins etc.
• Known fructose-intolerance or malabsorption
• Known allergy to one of the study drugs