The role of diet in determining glucose intolerance and its progression towards T2DM has been extensively investigated. A 2017 meta-analysis showed that a vegetarian diet is inversely associated with the risk of developing diabetes. Vegetarians, with the same baseline risk, are half as likely to develop T2DM than those following an omnivorous diet. Therefore, vegetarian nutrition could have important clinical implications in the dietary management of diabetic patients.

The primary objective of the study is to evaluate the effect of two different isocaloric meals, one vegetarian compared to a conventional Mediterranean-type one (vegetable protein source in the first case and animal in the second case), eaten at lunch, 1÷3 weeks apart, on the pathophysiology of glucose and insulin response. The two meals were elaborated in such a way as to have a superimposable composition.

Study population: 20 patients diagnosed with T2DM and BMI ≥ 30, belonging to the Diabetes and Clinical Nutrition clinic of the IRCCS San Raffaele Hospital.

Study design: single-center, interventional, controlled, randomized crossover.

Procedures: the patients enrolled in the study, for each of the two meals, underwent serial blood tests, before eating lunch (T0) and every 30 minutes, up to 3 hours after the end of the meal itself (T2÷T6).

Collected variables: blood sugar, insulin, c-peptide, HbA1c, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, height, weight, waist circumference and blood pressure, visual analogue scale (0-10) for sense of hunger and satiety , meal satisfaction index (0-10).

Inclusion Criteria:

• Age 18-70 years
• Diagnosis of T2DM
• In treatment with diet alone or single oral drug metformin
• BMI ≥ 30
• HbA1c between 6.0 and 9.0% (42-75 mmol/mol)
• Signature of the informed consent

Exclusion Criteria:

• History of acute/chronic pancreatitis
• Pancreatic cancer
• Pancreatic surgery
• Renal failure (any stage)
• Liver cirrhosis
• Thyroid disorders (hypothyroidism, hyperthyroidism)
• Patients with weight loss in the last 3 months equal to or greater than 5% of body weight
• Patients on therapy other than metformin monotherapy (insulin, glucagon-like peptide agonists, sulphonylureas, glitazones, dipeptidyl peptidase inhibitors, SGLT2 inhibitors).
• Pregnant or breastfeeding women
• History of severe allergic reaction to any food (anaphylaxis)