Gastric bypass surgery is a drastic operation that re-routes the digestive system to make food pass from the oesophagus straight to the small intestine. It is used as a successful obesity treatment and is the only form of weight loss surgery that has long-lasting results. People who have a gastric bypass lose weight and they keep it off.
“Doctors have noticed that many patients who have this operation are also cured of type 2 diabetes, and quickly. It has been a real puzzle why blood sugar levels normalise within days, before the patient has even lost any significant amount of body fat,” explains Dr Mark Vanderpump, Consultant Physician and Endocrinologist at The Physicians’ Clinic.
Research just published in Science has solved that puzzle. By studying the effects that a gastric bypass had on the intestine, Nicholas Stylopoulos and his group at Harvard Medical School showed that the surgery changes the way the intestine takes up and uses glucose.
When the operation is performed, the re-routing exposes the small intestine to undigested food rather than food that has already been processed in the stomach. This stimulates the cells in the intestine to take up more glucose and then to use it to repair the tissue that has been damaged by the surgery.
In the first few days after the operation the intestine becomes a major ‘sink’ for glucose, removing more of it from the blood, so reducing the high blood sugar typical of type 2 diabetes.
As time goes on, the rapid and consistent weight loss decreases insulin resistance and provides a long-term improvement that prevents type 2 diabetes returning.
What causes type 2 diabetes?
People with type 2 diabetes have trouble controlling the level of glucose in the blood. This type of diabetes usually comes on later in life, after the age of 40 and is not due to a lack of insulin.
"Around four in five patients with type 2 diabetes are overweight,” explains Dr Vanderpump. “They develop high levels of blood glucose not because they lack insulin but because their cells don’t respond to it. Insulin normally forces cells to take glucose out of the blood but insulin resistant cells ignore that signal.”
Type 2 diabetes is often not treated by insulin injections, particularly when first diagnosed. “Improving insulin sensitivity by eating a healthier diet and exercising more and by taking medications such as Metformin and GLP-1 agonists can help to control blood sugars,” says Dr Vanderpump.
Type 2 diabetes and weight loss surgery
“We now have significant evidence to suggest that weight loss surgery techniques can be very beneficial in patients whose body mass index is over 35. However it is not often seen as an option by patients as they perceive the risk of surgical intervention to be too great, even though the impact on type 2 diabetes can be dramatic.”
“This study has investigated the observation that diabetes can be ‘cured’ following gastric bypass surgery even before any significant weight loss is seen. The findings reveal the changes in the small intestine that are probably responsible for this. If we can find a way to replicate this using medicines rather than surgery, we may be able to develop a new, far more effective treatment for type 2 diabetes.”