What is Metabolic Surgery?

Metabolic surgery is the most effective and long-lasting treatment for type 2 diabetes, heart disease, hypertension and sleep apnea. Studies show bariatric surgery may reduce a patient’s risk of premature death by 30-50%. Bariatric surgery is as safe or safer than some of the most commonly performed surgeries in America including gallbladder surgery, appendectomy and knee replacement.

In June 2016, Diabetes Care published guidelines for metabolic surgery, positioning it as an important treatment option for patients with type 2 diabetes [1]. The guidelines were developed and ratified by the American Diabetes Association (ADA), the International Diabetes Federation, Diabetes UK, the Chinese Diabetes Society, and Diabetes India, and, at the time of publication, had been formally endorsed by an additional 40 diabetes, obesity, and surgical societies.

In contrast to bariatric surgery, metabolic surgery is intended to specifically address diabetes that fails to respond to lifestyle and medication changes, rather than obesity per se. Whereas bariatric surgery is generally performed in patients with a body mass index (BMI) of at least 40 kg/m2 (or ≥35 kg/m2 with comorbidities), the STAMPEDE metabolic surgery clinical trial in patients with type 2 diabetes included participants with BMIs as low as 27 kg/m2 [2].

The recent metabolic surgery guidelines do not drop the BMI threshold as far as the STAMPEDE investigators did, instead opting for 30 kg/m2 (27.5 kg/m2 for Asians). They also advocate a first-line glycemic control strategy of medication and lifestyle intervention for all patients with a BMI below 40 kg/m2. The management algorithm (see figure) advises physicians to consider surgery for patients with class I obesity (30.0–34.9 kg/m2) and poor glycemic control despite nonsurgical interventions, and for class II (35.0–39.9 kg/m2) obese patients even if they have good glycemic control. The ADA adopted the same thresholds in the obesity management section of the 2017 update to the Standards of Care [4] and the UK’s National Institute for Health and Care Excellence has endorsed a similar approach since 2014 [5].

Most middle- and high-income countries are in the grip of a “diabesity” crisis. During 2011–2014, 36.5% of adults in the USA were obese [6] and in 2012, 9.3% had diabetes, with nearly a third of these being undiagnosed [7], and recent data show rising diabetes rates in American youths [8].

Obesity is tough to combat using behavioral interventions, with studies such as Look AHEAD and the Diabetes Prevention Program Outcomes Study showing only moderate weight loss and frequent weight regain [9, 10]. Likewise, many diabetes patients struggle to control blood sugar and other metabolic risk factors, despite a wide range of available pharmacologic options. For example, only 65.7% of type 2 diabetes patients in England and Wales achieved a glycated hemoglobin (HbA1c) target of 7.5% (58 mmol/mol) in 2015–2016, and only 40.2% achieved all three of their key HbA1c, blood pressure, and cholesterol treatment targets [11]. Likewise, in the USA data for up to 2010 show just over half of patients achieving the ADA HbA1c goal of 7.0% [12, 13].

But controlling weight in diabetes patients is highly beneficial, with a recent analysis of the Look AHEAD study showing a significantly reduced risk for major cardiovascular disease outcomes among participants who lost weight [14].

Historic studies of bariatric surgery have revealed remission of type 2 diabetes in many patients undergoing the procedure [15, 16], which led to a flurry of trials that specifically recruited patients with diabetes [2, 17–24]. One of the first to appear, in JAMA in 2008, recruited 60 patients with BMIs between 30 and 40 kg/m2 and found 2-year diabetes remission in 73% of those who underwent gastric banding versus 13% of those given conventional treatment [17].

More recent studies include the aforementioned STAMPEDE trial, which included 140 patients with a BMI of 27 to 43 kg/m2 and reported 12-month HbA1c levels of 6.0% or less in around 40% of patients who underwent surgery (gastric bypass or sleeve gastrectomy), compared with 12% of those who received medical therapy [2]. At the same time, between half and three-quarters of the surgical patients did not require diabetes medications, whereas all patients in the medical therapy group required at least one.

Another notable trial, being one of the largest per treatment group, is the Diabetes Surgery Study Randomized Clinical Trial, published in JAMA in 2013 [24]. This targeted patients with BMIs between 30.0 and 39.9 kg/m2 and reported that 49% of the 60 who underwent gastric bypass surgery met all three of the HbA1c (<7.0%), cholesterol, and blood pressure targets at 12 months, compared with 19% of the 60 in the medical management group.

Some of these metabolic surgery trials are beginning to yield longer-term data, with STAMPEDE and another trial that reported its initial results in the same year recently reporting their 5-year outcomes [25, 26]. Although some patients had relapsed by this time, the proportion who still met their glycemic targets, with or without diabetes medications, remained substantially larger for surgical patients than for medical intervention patients, at 23–29% versus 5% in STAMPEDE and 42–68% versus 27% in the other trial (which had a less stringent HbA1c target, of 6.5%).

Although a proportion of patients in these trials did relapse, several studies have described a “legacy effect” of a former period of good glycemic control, including as a result of surgery, with benefits seen for later glycemic and microvascular outcomes [27–29].

The evidence so far suggests that metabolic surgery is effective and relatively low risk, leading to its endorsement in multiple guidelines, but whether it will become “a mainstream treatment that most people with diabetes would accept is a totally different question,” says Wilding.

One barrier to its wider use is that the patients who can potentially benefit often have a poor opinion of the procedure and are unwilling to consider it. In a survey of 130 patients with diabetes and a BMI of 30–40 kg/m2, only about one in five looked favorably upon the idea of metabolic surgery, with most doubting its safety and efficacy, and a substantial proportion even believing that the procedure carried a moderate-to-high risk for death [39].

Author:

Dr Syed Imran Abbas

MD,FACS,FASMBS,FMIS

     Laparoscopic Bariatric & Metabolic Surgeon

    Iranian Hospital , Dubai,UAE

References

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