September 21, 2021

I, Science

The science magazine of Imperial College

'Weight-loss surgery' provides a potential road to permanent recovery from type II diabetes; Nicole Samuel explores..

surgeryAccording to a growing body of evidence, bariatric surgery could provide a long-term resolution for certain chronic diseases linked to obesity, such as heart disease and diabetes. This idea has now been corroborated by studies across the globe – most recently the National Registry of Bariatric Surgery Audit, which has looked at the results of all recent surgeries done on the NHS. As the prevalence of obesity skyrockets, these findings could provide a chance for people to escape a lifetime of deteriorating health.

Dubbed “weight-loss” surgery, bariatric techniques involve drastically limiting calorie consumption through stomach-size reduction or gastric bypasses. These surgeries tend to be used as a last-resort weight loss technique. However recent evidence suggests the long-term benefits can include the improvement of related conditions. Notably, Type-2 Diabetes can go into remission – an outcome currently impossible with medical therapy.

Type 2 diabetes is a chronic condition where the body’s ability to breakdown and store glucose is hindered. A diet high in carbohydrates and sugars requires that the body maintain high levels of the hormone insulin in order to keep damaging levels of glucose from circulating in the blood. Over time the body can develop resistance to insulin and simultaneously there is a decrease in insulin production. This leads to high blood glucose, which has detrimental effects throughout the body and increases the risk of heart disease, strokes and kidney failure, amongst others.

However post-surgery there is an immediate improvement in glucose control with a return to normal glucose metabolism over time. Although it is still unclear exactly what causes this recovery the current theories identify two main components to the body’s response.

The first involves changes in gut hormone release. Following bypass surgery, the arrival of undigested food in the small intestine increases the production of the hormones peptide YY, oxyntomodulin and GLP-1. The first two reduce appetite and contribute to satiety. The key player is GLP-1. Its immediate effect is to stimulate insulin release and reduce appetite. Longer term, it increases the insulin producing capacity so that greater amounts are released over time, enhancing its effect.

The second process occurring post-bariatric surgery links the reduction in calorie consumption with increased insulin sensitivity. Following surgery, patients begin to burn more calories than they consume – this extra energy comes from the breakdown of stored body fat, especially associated with the liver. Liver fat levels are closely linked to the organ’s insulin sensitivity: as fat levels drop, insulin sensitivity rises. This rise in insulin sensitivity allows the liver to take up and store large amounts of glucose, thereby lowering the amount in the blood.

What are the long-term effects of bariatric surgery for diabetic patients? Amazingly, glucose metabolism can return to normal and the diabetes is effectively cured. Previously diabetics faced a lifetime of tablets and injections, and the knowledge that the disease could contribute to an early death. Now, for the first time, there is an alternative: one that can improve someone’s quality of life and their health in the long term.