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Metabolic surgery: Effective, safe treatment for diabetes?

The primary risk factor for type 2 diabetes is excess weight; 90% of all patients with type 2 diabetes are overweight or obese. If bariatric surgery is one of the most effective treatments available for extreme obesity, can it also have a role to play in the treatment of diabetes?

That is the question that health care professionals, patient advocates and health care policy-makers grappled with at the first Canadian Summit on Metabolic Surgery for Treating Type 2 Diabetes in May, 2010, in Montreal. Mounting evidence indicates that bariatric surgery significantly reduces morbidity and mortality, is safe, and will save the health care industry billions of dollars. But the procedure also requires lifelong follow-up and has waiting lists of up to a dozen years or more.

“Emerging research shows that 80% of morbidly obese patients with type 2 diabetes experience tremendous improvements in their blood glucose levels after bariatric (or “metabolic”) surgery,” says Dr. Nicolas V. Christou, Professor of Surgery at McGill University in Montreal and lead organizer of the Summit.

Dr. Christou cites a meta-analysis published in the  American Journal of Medicine  (March 2009), which analyzed 621 studies from 1990 to 2006. The results showed that 78.1% of patients with type 2 diabetes had complete resolution of their disease, while a total of 86.6% of patients experienced improvement or resolution of their diabetes as the result of bariatric surgery. Researchers observed a progressive relationship of diabetes resolution and weight loss as a function of the operation performed: laparoscopic adjustable gastric banding, gastroplasty, gastric bypass, and biliopancreatic diversion/ duodenal switch (BPD/DS). 

Gastric banding yielded 56.7% resolution, gastroplasty 79.7%, gastric bypass 80.3%, and BPD/DS 95.1%. After more than two years post-operative, the corresponding resolutions were 58.3%, 77.5%, 70.9%, and 95.9%. In addition, the per cent excess weight loss was 46.2%, 55.5%, 59.7%, and 63.6%, for the type of surgery performed, respectively.

While bariatric surgery’s efficacy in treating type 2 diabetes is well documented, researchers are still not clear as to why it works.

“Most studies point toward the rearrangement of gastrointestinal anatomy as a primary mediator of the surgical control of diabetes,” says Dr. Christou. “Bypass surgery may somehow alter the hormonal milieu, reduce hunger, and improve insulin resistance. Perhaps insulin production is also being stimulated. We still need more research in this area.” 

In terms of safety, the short-term perioperative risk (those associated with the time spent preparing for, undergoing, and recovering from surgery) of bariatric surgery has been shown to be no higher than the risk of other types of major surgery in severely obese patients. In 2009, the US Longitudinal Assessment of Bariatric Surgery (LABS) Consortium published the results of its prospective, multicentre, observational study, describing the 30- day outcomes of 4,776 participants who received either a Roux-en-Y gastric bypass or underwent laparoscopic adjustable gastric banding. The 30-day rate of death for all patients was 0.3%; 4.3% of patients had at least one major adverse outcome. The risk was lower in banding patients. The risk was highest for patients with a history of deep vein thrombosis or pulmonary embolus, a diagnosis of obstructive sleep apnea, impaired functional status, and an extremely high BMI.

Cost-savings projected

Bariatric surgery doesn’t just save lives, it may also save money. An Australian cost effectiveness
study comparing therapies for obese patients with recently diagnosed type 2 diabetes found that surgically induced weight loss was associated with a mean health care saving of approximately $2,240 CDN per patient compared to conventional diabetes management.

The Canadian Diabetes Association estimates that by 2020, one in 10 Canadians will have diabetes, representing an economic burden of approximately $16.9 billion.

“Adding bariatric surgery to the armamentarium of treating diabetes could significantly reduce the health care expenditures of our cash-strapped provincial and federal governments,” says Dr. Christou.

Bariatric surgery for type 2 diabetes isn’t without its downsides, however. As Dr. Arya M. Sharma, Scientific Director of the Canadian Obesity Network, recently wrote, “Done in the wrong patients with no or little long-term follow up, what could be a life-saving operation can become a disaster.”

In addition to weight regain and poor glycemic control, poor outcomes can include nutritional deficiencies, and psychological and social dysfunction. Dr. Christou agrees that long-term follow up is mandatory for all bariatric surgery patients to ensure proper vitamin supplementation.

“Follow-up is at least as important as the surgery itself,” he explains. Perhaps the greatest negative associated with bariatric surgery is the severely limited access to the procedure. A cross-Canada survey conducted in 2007-2008 revealed that the average wait for bariatric surgery is 5.2 years. Dr. Christou’s clinic at McGill University Health Centre is the busiest in Canada, with a waiting list up to 13 years long. “Clearly, accessibility needs to be addressed,” he says.

Dr. Sharma adds that accessibility of these surgical programs requires more than just adding surgeons and operating room time. Dietitians, psychologists, physicians, occupational therapists, social workers, and other health professionals who are trained and qualified to prepare and follow up with surgical patients are also needed.

“To optimally care for patients struggling with the immense burden associated with severe obesity — including type 2 diabetes — we must ensure that they are able to access state-of-the-art standards of care in a timely and equitable fashion,” says Dr. Sharma.