It may seem strange that something like bariatric surgery could help patients with Type 2 diabetes. After all, it doesn’t involve modifying the pancreas where insulin is produced. But evidence continues to accumulate showing that weight-loss surgery does help patients who have diabetes mellitus or its precursor, insulin resistance. Even patients who don’t currently have diabetes can substantially reduce their risk for developing the disease over time with surgically assisted weight loss.

How Does Weight-Loss Surgery Help Restore Normal Blood Sugar?

There are actually many complex, interrelated functions that determine blood sugar levels. The pancreas has to produce enough insulin to manage glucose in the blood. Then, it has to work efficiently – something that doesn’t happen in insulin resistant patients due to hormones and enzymes that block the action of insulin. Receptor cells in the liver and muscles may also become less responsive to insulin, limiting the body’s ability to break down sugar in the blood stream. The less sensitive the body is to insulin, the more insulin the pancreas must produce to bring blood sugar down to normal levels. The beta cells in the pancreas that produce, store and release insulin can eventually wear out due to being overworked year after year.

Obesity is one well-known factor that increases the risk of hormonal imbalance related to diabetes. Fat in the liver and muscles in particular is associated with poor insulin sensitivity. Overeating (especially simple carbs like sugar) puts stress on the pancreas by forcing it to churn out insulin at high levels.

Bariatric surgery may improve the body’s blood sugar by:

  • Supporting dramatic weight loss over the long term, helping the body produce less of the hormones that can interfere with insulin in the bloodstream
  • Reducing fat content in the liver, improving insulin sensitivity with even relatively minor weight loss
  • Encouraging adherence to a nutritious diet low in simple carbs and high glycemic index foods

Surgeries such as sleeve gastrectomy and gastric bypass that remove part of the stomach also dramatically reduce the body’s ability to produce ghrelin. This is a hormone that causes sensations of hunger, and it is also linked to insulin resistance. The result of a drop in ghrelin hormone is almost instantaneous. It may explain why gastric bypass patients sometimes experience immediate normalization of blood glucose levels after surgery – before they lose any weight at all.

Studies Show Benefits and Limitations of Bariatric Surgery’s Affect on Diabetes

2012 Institute of Medicine in Gothenburg, Sweden

This study followed obese patients for 15 years to track the incidence of diabetes in those who underwent WLS vs. those who did not. The results showed that bariatric surgery is remarkably more effective than traditional medical treatment for preventing Type 2 diabetes in at-risk patient populations. The results were calculated in “person years” and showed patients in the non-surgery group had four times the risk of developing diabetes compared to those who had surgery.

Cleveland Clinic STAMPEDE Study 2013

This study followed outcomes for 150 patients who were already diagnosed with Type 2 diabetes and managing it with several medications. At the one year mark, more than 42 percent of patients who had gastric bypass achieved and maintained normal blood sugar levels (about 37 percent for gastric sleeve patients). Only 12 percent of medication-only patients achieved the same results. All of the gastric bypass patients were able to stop taking medications for diabetes. About three out of four gastric sleeve patients also had normal blood sugar without meds. Bypass in particular appears to help restore pancreatic function and reduce belly fat that interferes with insulin usage.

Group Health Research Institute, Seattle WA 2013

A 10-year study of more than 4,400 patients has confirmed that not all patients experience remission or improvement of diabetes after weight-loss surgery. Even though 68 percent of patients in this study experienced total remission of diabetes, one-third of those patients suffered a recurrence within five years. In all, only about 44 percent of gastric bypass patients appear to have long-lasting remission. Patients who have been living with advanced diabetes for many years seem most likely to experience recurrence or have no improvement. The amount of sustained weight loss did not correlate to the risk of diabetes returning in this study. It appears that earlier intervention, before irreversible damage occurs to the pancreas, may be associated with better outcomes.

Conclusions for Potential Bariatric Surgery Patients

Many patients with diabetes or pre-diabetes may experience dramatic improvement in their body’s ability to produce and use insulin after bariatric surgery. However, the hope that diabetes will disappear should not be the only consideration in determining whether weight-loss surgery is the right cho