For type 2 diabetes, mainly as a result of increased fat in the target organs for insulin resistance is caused by a chronic metabolic disease. The insulin resistance, blood sugar levels within the normal range at the start to maintain the pancreas to secrete more of the hormone causes. However, in the course of the disease, giving rise to a lack of insulin is not the exhaustion of the gland.
Bariatric surgery not only helps in weight loss but it also leads to remission of diabetes in the majority of people. Procedures that induce greater weight loss are associated with higher rates of diabetes remission.
The three main mechanisms of diabetes remission after bariatric surgery are
1. Weight loss ( predominantly loss of body fat)
2. Accelerated gastric emptying
3. Increased contact of undigested food with the distal small intestine
Weight loss – Body fat, predominantly the visceral adipose tissue, is a major risk factor for metabolic diseases and insulin resistance. This produces inflammatory cytokines which cause hyperglycemia, hyperglycemia and atherosclerosis leading to diabetes, hypertension, coronary artery disease and stroke. Due to loss of body weight and reduction of visceral fat, there is both a decrease in insulin demand within the body as well as a decrease in the peripheral insulin resistance. This is particularly helpful in those people with type 2 diabetes who basically have elevated insulin levels due to peripheral insulin resistance. The insulin levels have shown to be normalized after surgery with increased sensitivity of target tissues to insulin giving rise to normal blood sugar levels.
Accelerated gastric emptying- Most of restrictive procedures including sleeve gastrectomy and adjustable gastric banding cause the gastric emptying time to be shortened which leads to increased exposure of the small intestine to undigested food.
Malabsortive procedures- The Malabsortive procedures cause undigested nutrients to come into direct contact with the small intestine. This causes rise in the levels of certain gut hormones known as incretions such as GLP-1. These hormones in turn stimulate insulin secretion from the pancreas. Increased insulin also up regulates the metabolism and causes more stored fat to be utilized for energy. As a consequence, weight loss is accelerated and it leads to diabetes remission.
Various studies and Meta analyses have shown normalization of fasting blood sugar/HbA1C levels in the majority of diabetic patients with long term improvement/remission of the disease. Comparative trials of bariatric surgery versus intensive medical treatment for remission of type 2 diabetes in obese people with BMI 30-40 kg/m2 (Dixon et al) have shown that surgical therapy was associated with significantly higher rate of diabetes remission (73% vs. 13%) and weight loss (20.1% vs 1.3%) as compared to medical treatment after 2 years Similar studies by Schauer and Migrone et al have shown significant remission of diabetes with decrease in medication after bariatric surgery
The rate of diabetes remission after bariatric surgery is determined by the type of procedure. It has been shown to be highest for Malabsortive procedures like BPD-DS and RYGB (> 50% remission in some studies) and is lesser for restrictive procedures like sleeve gastrectomy and gastric banding. The rate of diabetes remission is also determined by patient related factors. Those people with long standing diabetes, insulin use and poor blood sugar control pre operatively were found to have less rates of remission compared to other subjects