Overweigth and obesity are commonly diagnosed in children with type 1 diabetes, and frequently an increase of wiegth and BMI is observed after diagnoses. Hybrid cloosed loop system are new system where insulin is continually adapted to glycemia (using an algorythme). The weight and growth trajectory of children treated with this system is poorly described.

Unlike type 2 diabetes, which is a frequent metabolic complication of obesity, type 1 diabetes is not a consequence of overweight or obesity, or of an excessively sweet or unbalanced diet.

However, more and more studies are linking type 1 diabetes to obesity. An international study with 23 026 children suffering from type 1 diabtes has shown that 22.3% of boys and 27.2% of children have overweight, and 6.8% and 6.3% respectively obesity . Several hypothesis are made to explain this trend : a consequence of intensive insulinotherapy, the fear of hypoglycemia with unnecessary glucose intake, the increase of caloric intake and the decrease of physcial activity. Moreover, subcutaneous insulinotherapy leads to modification in body composition with a increase in fat mass . Nevertheless, some studies highlights a possible role of obesity in the type 1 diabetes development( familial history of type 2 diabetes more common in children with type 1 diabetes , inverse relation with age at diagnosis and BMI suggesting that children with higher BMI will be diagnosed early in age .

Hybrid closed-loop systems, in which the insulin flow rate is adjusted almost instantaneously to the blood glucose level by using an algorithm with a CSII and a CGM, are new systems that have gradually been used in current practice . These systems are significantly associated with an improvement in glycemic control (HbA1C and TIR)[17], a reduction in the time spent in hypoglycemic states , and with an improvement in quality of life.

Nevertheless, the impact of this new treatment on weight evolution has been poorly described. A previous study with 50 children included did not show a BMI modification after 1 year of treatment. Individually, some patients following in our center have shown a reduction of BMI after treatment of type 1 diabetes with with hybrid closed loop system.

This leads us to perform an observational study in order to describe the trajectory of BMI and growth parameters of children suffering from type 1 diabetes (expressed in standard deviations (SDS) after 6 months, 1 year and 2 years of treatment with hybrid closed loop system in the university hospital of Nancy. The second objective is to identify potential factors associated with the positive evolution of BMI at 6 months, 1 year and 2 years.

Inclusion Criteria:

• children between 6 and 18 years at the beginning of treatment with HCL
• type 1 diabetes
• follow up in University Hospital of Nancy between 01/01/2021 - 31/12/2023
• treatement with HCL since 6 months

Exclusion Criteria:

• parental opposition for the study
• pregnancy

children with type 1 diabetes follow up in Hospital of Nancy with HCL since 6 months minimum