Effects of diet-induced weight loss and Roux-en-Y gastric bypass on the glycemic and gut hormones profile in patients with severe obesity and diabetes

Objectives  The mechanisms following glycemic control after RYGB are still not fully elucidated. The objective of the present study was to compare the effects of similar weight loss induced by a Very Low Calorie Diet (VLCD) and by Roux-en-Y Gastric Bypass (RYGB) on the glycemic and gut hormone profile in patients with severe obesity and T2DM.

Methods  A prospective controlled observational study with 10 patients evaluated before (pre-0), after 10 % weight loss induced by VLCD (pre-1), and after 10 % weight loss induced by RYGB (post). Oral Glucose Tolerance Test (OGTT) was performed in pre-0 and pre-1. In all periods, glycemic (glycemia, insulin) and gut hormone profile (Ghrelin, GIP and GLP1) were evaluated in fasting condition (T0) and 30-, 60-, 90- and 120-minutes after a standard meal (Nutren 1.5®).

Results  After 10 % weight loss induced by VLCD 5 patients had remission of T2DM in OGTT. There was a significant increase in ghrelin levels after 10 % weight loss with VLCD (pre-1; p < 0.001). There was no difference in GIP levels. There was a significant increase in GLP1 levels between pre-0 and pre-1 (p < 0.004) at T0 and between pre-1 and post at all times after a standard meal (p = 0.01; p = 0.002; p = 0.002; p = 0.01; p = 0.04).

Conclusions  50 % of patients had glycemic control after diet-induced weight loss. After RYGB, all patients had improved glycemic control. The increase of GLP1 after weight loss induced by metabolic surgery is responsible for glycemic control.

Keywords
Diabetes mellitus; Incretins; Very low calorie diet; Glucagon-like peptide-1