To assess whether the DIABELOOP algorithm provides better glycemic control than the usual algorithm of T1D patients on pump therapy:

• at meals, with CHO roughly assessed by the patient.
• during and after physical activity sessions qualified as moderate by the patient.

Primary endpoint : time within the glycemic reference range. The study will be conduct with 15 patients at the following investigation centers : Corbeil Hospital, CHU of Grenoble, and CHU of Montpellier.

The 15 patients will have 2 visits during 24 hours (day and night), once with their usual algorithm and once with the Diabeloop system.

Inclusion Criteria:

• Patient type 1 diabetic for at least one year
• Patient treated by external insulin pump for at least 6 months
• Patients with HbA1c <9%
• Patient affiliated with Social Security.
• Patient able to perform two tests of physical activity of 30 minutes (one event in each treatment period);
• aged at least 18 years Patient;
• Patient who signed consent

Exclusion Criteria:

• All serious disease that could interfere with the study
• BMI > 30 kg/m2
• insulin requirement > 2 U/kg/day
• Patient benefiting from a measure of legal protection;
• Pregnant or likely to be women.