Sleeve gastrectomy is a restrictive procedure based on the removal of a large part of the gastric fundus. According to a recent randomized study, weight loss and resolution of diabetes are comparable to that obtained after gastric by-pass (79.7 % versus 80.3%), but with a lower morbidity. The mechanisms involved in the rapid resolution of diabetes after sleeve gastrectomy remain poorly understood, as no specific study in patients with type 2 diabetic obese are available. An increase in post- absorptive levels of Glucagon-like Peptide 1(GLP-1), Peptide YY(PYY) and insulin has been reported, but in non-diabetic subjects mostly. The important caloric restriction in the early postoperative period indeed improves hepatic insulin resistance, regardless of weight loss. Specific metabolic and hormonal effects of this surgical procedure cannot be excluded.The aim of our study is to explore the early and late metabolic effects of sleeve gastrectomy in severely obese patients with non-insulin-treated type 2 diabetes. We will also evaluate insulin sensitivity, insulin secretion and incretin effect. We will include 14 obese patients with type 2 diabetes, considered eligible to bariatric surgery according to HAS criteria, and whose diabetes treatment involves only metformin, sulfonylurea and glinides. They will be randomized to a 1-week caloric restriction period or no caloric restriction, immediately before surgery. Test meals with dosages of blood glucose, insulin, C-peptide, adiponectin, leptin, GLP-1, PYY and ghrelin will be performed before and after caloric restriction, and 1 week, 3 month, 6 month and 12 month after surgery.

Inclusion Criteria:

• written informed consent
• Age between 18-65 years (inclusive)
• Men or women receiving effective contraception, postmenopausal or sterile
• type 2 diabetes treated with no drugs or oral anti-diabetic agents metformin, sulfonylurea or glinides
• Body mass index 35 kg / m² or above
• eligible to bariatric surgery according to HAS criteria

Exclusion Criteria:

• Treatment of diabetes with GLP1 analogues, DPP-IV (dipeptidyl-peptidase IV) or insulin
• Treatment with drugs that modify glucose homeostasis: glucocorticoids, anorexigens, antihistaminics, psychotropic drugs especially serotonergic antidepressants (except for the occasional use of a hypnotic or anxiolytic), atropine, laxatives, thyroid hormones (with the exception of a substitution dose ensuring a stable euthyroid at baseline), beta blockers, diuretics
• Pregnancy, intention of being pregnant, breastfeeding.
• Inability to understand the nature and aims of the study or to communicate with the investigator- High probability of non
• compliance with the protocol
• Simultaneous participation in another trial
• No affiliation to the French social security
• Loss of personal capacity resulting in state protection
• Deprivation of liberty by judicial or administrative decision