Due to COVID-19 related challenges and restrictions, the project could not be launched as planned. Meanwhile, the current state of research has changed and the initialisation of the project is no longer appropriate. No participants were recurited.

To investigate the efficacy, safety and utility of hybrid closed-loop glucose control during a low carbohydrate vs. iso-energetic balanced diet in individuals with type 1 diabetes.

Closed-loop systems combining an insulin pump, a glucose sensor and a dosing algorithm that adjusts insulin delivery in a glucose-responsive manner achieve significantly better glucose control than conventional therapy in type 1 diabetes. Achieving satisfactory postprandial glucose control, however, continues to be challenging. The main limitation is the delayed pharmacokinetics and -dynamics of subcutaneously administered insulin with peak actions between 1 and 2 hours. Conversely, glucose levels typically rise within 10minutes following carbohydrate intake. This mismatch largely explains the inability of current closed-loop systems to control postprandial glucose excursions and the increased risk of late postprandial hypoglycaemia in response to both user-derived meal bolus administration and reactive algorithm-driven insulin infusion.

Restricting carbohydrate may therefore significantly improve post-prandial glucose control whilst reducing hypoglycaemia. The efficacy of hybrid closed-loop operation in individuals with type 1 diabetes adhering to a low carbohydrate compared to a iso-caloric balanced diet has not been investigated to date.

Inclusion Criteria:

• Female and male subjects aged 18 years or older
• Diabetes mellitus Type 1 as definded by WHO for at least 2 years or C-peptide negative (<100 pmol/L with concomitant blood glucose > 4 mmol/L)
• hybrid-closed-loop Insulin therapy (Minimed 670G) for at least 2 months
• HbA1c <= 9 %
• The subject is willing and capable of adhering to the diet plan.

Exclusion Criteria:

• Physical or psychological condition likely to interfere with the normal conduct of the study and interpretation of the study results as judged by the investigator.
• Excess alcohol consumption (> 3 units/day for men, > 2 units/day for women)
• Pregnancy, planned pregnancy or breast feeding
• Current participation in another clinical trial
• Total daily insulin dose >2 IU/kg/day
• Nephrolithiasis
• Hereditary dyslipidemia
• Liver steatosis