Weight loss surgery is not a cure for type 2 diabetes, but it can improve blood sugar control, according to a new study published in the British Journal of Surgery. Whereas some previous studies have claimed that up to 80 per cent of diabetes patients have been cured following gastric bypass surgery, researchers at Imperial College London found that only 41 per cent of patients achieve remission using more stringent criteria.

The research was funded by the National Institute for Health Research (NIHR) Biomedical Research Centre awarded to Imperial College Healthcare NHS Trust and Imperial College London.

Obesity is a major risk factor for type 2 diabetes. Worldwide, 80 per cent of people with type 2 diabetes are overweight or obese at the time of diagnosis. Diabetes is normally treated by using insulin injections and drugs to control blood sugar. However, many diabetic patients who had stomach surgery to lose weight found that their diabetes improved, even before they had lost any weight.

Recently the American Diabetes Association pulled together a group of experts to agree on standards by which to assess whether a patient has achieved remission of diabetes. They defined complete remission as returning to normal measures of glucose metabolism without taking diabetes medication at least one year after surgery.

The new study revisited previous data on 209 patients with type 2 diabetes to evaluate the effectiveness of three types of weight loss surgery using the new criteria. They found that the remission rate was 41 per cent for gastric bypass, the most effective type of surgery.

"Using the new criteria, we don't get such eye-catching figures as some that have been quoted in recent years," said Dr Carel le Roux, from the Department of Medicine at Imperial College London, who led the study. "But it's clear that weight loss surgery, particularly gastric bypass, has a significant beneficial effect on glucose control.

"Diabetes is a chronic, multisystem disease. Stomach surgery may not mean that patients can stop taking diabetes medication, but surgery and medication together achieve better results than either treatment on its own."

Gastric bypass involves stapling the stomach to create a small pouch at the top, which is then connected directly to the small intestine, bypassing most of the stomach and the duodenum (the first part of the small intestine). Sleeve gastrectomy, which involves surgically removing a portion of the stomach, and gastric banding, in which a band is placed around part of the stomach, achieved remission rates of 26 per cent and 7 per cent respectively, although these figures are based on smaller numbers of patients.

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More information: DJ Pournaras et al. 'Effect of the definition of type II diabetes remission in the evaluation of bariatric surgery for metabolic disorders.' British Journal of Surgery, Volume 99, Issue 1, pages 100, January 2012 Journal information: British Journal of Surgery DJ Pournaras et al. 'Effect of the definition of type II diabetes remission in the evaluation of bariatric surgery for metabolic disorders.', Volume 99, Issue 1, pages 100, January 2012