Very low-carbohydrate ketogenic diet before bariatric surgery: prospective evaluation of a sequential diet.

Background We evaluated the effectiveness of a sequential diet regimen termed the obese preoperative diet (OPOD) in morbidly obese patients with and without type 2 diabetes mellitus (T2DM) scheduled for laparoscopic bariatric surgery. Methods Fifty patients (body mass index 53.5 ± 8.4 kg/m2) scheduled for bariatric surgery, including 14 with T2DM, were prospectively enrolled and followed the OPOD regimen: a very low-calorie ketogenic diet for 10 days, followed by a very low-calorie diet for 10 days, and then a low-calorie diet for 10 days. Patients were evaluated at baseline (T0) and after 10 days (T1), 20 days (T2), and 30 days (T3). Results Body weight, body mass index, waist circumference, and neck circumference were significantly lower at T1, T2, and T3 than at T0 in the 48 patients who completed the OPOD. Two patients discontinued the OPOD after 4–7 days. In patients with T2DM, fasting plasma glucose levels decreased significantly, enabling reduction of diabetic medications. Plasma and urine ketone levels increased at T1 but were all