Low Carbohydrate Diet (LCD) (< 130 g of carbohydrate per day) and ketogenic diet (< 50 g of carbohydrate per day) are popular among patients with type 1 diabetes (T1D). In most cases, LCD allow a better glycemic control and a important decrease of insulin requirements that cannot, however, be the sole result of low carbohydrate intake. However, due to the increase production of ketone bodies and the decrease of the insulin/glucagon rate, this diet is not without risk in T1D patients and some of them develop ketoacidosis.

Type 1 diabetes is a autoimmune disease defined by the destruction of the pancreatic beta cells by the effector T cells, in condition of low regulatory T cells (Tregs). Indeed, some nutrients could regulate the plasticity and the function of Tregs, and be involved in the control of some autoimmune diseases in animals models thanks to a direct effect on immune cells of the digestive tract or an indirect effect by microbiota modulation.

The study hypothesises that LCD may be able to restore residual insulin secretion in some patients by modulating immunity. The metabolic mechanisms leading to the effects described in patients with T1D patients under LCD have not been studied : in particular, there is no data on the evolution of the residual insulin secretion and no immunological parameter has been studied on these patients.

Inclusion Criteria:

• 18 years old or older
• type 1 diabetes for less than 20 years
• willing to start a low carbohydrate diet of less than 75 g per day
• under continuous glucose monitoring
• having been informed about the study and having given their written and informed consent

Exclusion Criteria:

• already on a low carbohydrate diet of less than 100 g per day
• history of ketoacidosis within the last 5 years, except during diabetes diagnosis
• autoimmune disease, except thyroiditis
• immunosuppressive treatment
• hepatitis B virus, hepatitis C virus or human immunodeficiency virus infection
• ongoing cancer or history of cancer within the past 5 years, except in situ cervical cancer or basal cell cancer with early treatment
• participation to another interventional study within the past 3 months
• pregnancy or breast feeding
• no affiliation to a social security scheme
• patients subject to legal protection measures
• unability to give consent for the study