Type 2 diabetes and obesity travel together. Excess body fat, especially around the abdomen, makes the body resistant to insulin, and the pancreas gradually fails to keep up. Medicines, diet and exercise remain the foundation of treatment. But for people with significant obesity, bariatric surgery has become one of the most effective treatments for type 2 diabetes available - so much so that it is now often called metabolic surgery. This article explains why it works, who it is for, and what it does not do.
It is not only about weight
The most striking observation from bariatric surgery is that blood sugar often improves within days of the operation - long before any meaningful weight has been lost. This tells us that the benefit is not simply "less fat, less insulin resistance". Rerouting or reducing the stomach changes the way the gut releases hormones after a meal:
- Food reaches the lower small intestine faster, which increases the release of GLP-1 and related hormones that boost insulin and reduce appetite (the same hormones that newer diabetes injections imitate).
- Signals from the upper intestine that worsen insulin resistance are reduced.
- Hunger hormones such as ghrelin fall after sleeve gastrectomy.
- Bile acid handling and gut bacteria change in ways that improve sugar metabolism.
Weight loss then adds to these effects over the following months, reducing fat in the liver and pancreas and further improving insulin sensitivity.
The operations
Sleeve gastrectomy removes about three-quarters of the stomach, leaving a narrow tube. It is the commonest bariatric operation in India, technically simpler, and produces good diabetes improvement in most patients.
Roux-en-Y gastric bypass creates a small stomach pouch and connects it directly to the small intestine, bypassing the rest of the stomach and the first part of the intestine. It has the strongest effect on diabetes, particularly in people with severe reflux or long-standing diabetes, at the cost of a slightly more complex operation and lifelong vitamin supplements.
Both are done laparoscopically (keyhole) and, in suitable patients, robotically at our hospital, with a hospital stay of two to three days. An endoscopic option, endoscopic sleeve gastroplasty, exists for people with lower BMI who are not candidates for surgery; its effect on diabetes is smaller.
What the results look like
In large studies and randomised trials comparing surgery with the best medical treatment, surgery has consistently produced greater improvement in blood sugar, more patients coming off diabetes medicines, and better blood pressure and cholesterol at five and ten years. Roughly speaking:
- A majority of patients achieve remission - normal HbA1c without medicines - in the first one to two years, with bypass somewhat ahead of sleeve.
- Remission is more likely when diabetes is recent (under five to eight years), when the patient is not yet on insulin, and when the pancreas still produces reasonable insulin.
- Some patients relapse over the years, particularly with weight regain; even then, diabetes is usually easier to control than before surgery.
- Complications of diabetes - kidney damage, nerve damage, heart disease - progress more slowly after surgery.
"Remission" is the honest word. It is not a cure; diabetes can return, and lifelong follow-up is part of the treatment.
Who is a candidate?
Indian guidelines recognise that Asian patients develop diabetes at lower body weights than Western populations. Broadly, surgery is considered for people with type 2 diabetes and a body mass index (BMI) of 32.5 or more, and in selected cases from a BMI of 27.5 when diabetes is poorly controlled despite good medical treatment. Every patient is assessed by a team - surgeon, physician or endocrinologist, dietitian - and the decision is made with you, never as a first step. Type 1 diabetes is different and is not treated with surgery.
What it does not do
- It does not replace diet, exercise and follow-up. Patients who ignore these regain weight and lose the benefit.
- It does not remove the need for lifelong vitamin and mineral supplements after bypass, and for regular blood tests after either operation.
- It carries surgical risk - bleeding, leak, clots, and later gallstones or nutritional deficiency - which is low in experienced centres but never zero.
- It is not suitable for everyone with diabetes, and it does not treat type 1 diabetes.
