If the 50 or so diabetes experts who convened in London in 2015 have any say in the matter, gastric bypass surgery will no longer be just for the obese. Through questionnaires, discussions and voting, the Second Diabetes Surgery Summit (DSS-II) put together guidelines for what they call “metabolic surgery” and published them in Diabetes Care in June 2016. In practice, these can be the same procedure used for weight loss, also known as bariatric surgery; however, surgeon Ricardo Cohen, coordinator of the Obesity and Diabetes Center at São Paulo’s Oswaldo Cruz German Hospital, advocates use of a distinct term to emphasize their different intent. “We don’t want to regulate the surgery; that [regulation] has been in place for decades,” explains the physician, who attended the DSS-II. “We want to include metabolic surgery in the algorithm for treating diabetes.”
The idea is to dissociate this type of surgery from a diagnosis of obesity, as international data show that 50% of type 2 diabetes patients have body mass indexes (BMIs) below 35 kilograms per square meter (kg/m2). Bariatric surgery is currently recommended for the morbidly obese, characterized by BMIs over 40 kg/m2, but may be approved for BMIs between 35 and 40 kg/m2 if the patient is diabetic or has severe cardiovascular problems. The proposed change in indication is based on hundreds of articles about the metabolic effects of bariatric surgery.
One of these studies was conducted by Cohen’s research group. It involved 66 patients with BMIs ranging from 30 to 35 kg/m2 and who had been diagnosed with diabetes 13 years earlier, on average. The subjects underwent bariatric surgery and were monitored for six years. The results, published in 2012 in Diabetes Care, showed improvements in diabetes indexes. At the end of the study, 88% of the patients continued to have no need for diabetes medication and 11% had relapsed, but to a milder case of the disease. According to the DSS-II article published in June 2016, patients who undergo gastric bypass surgery may remain diabetes-free for an average of eight years.
A larger-scale and more extended monitoring program was conducted in Sweden, where over 2,000 bariatric surgery patients were tracked for a period of 10 to 20 years and compared to a similar group who had received only clinical treatment. The study, known as Swedish Obese Patients (SOS), has been reporting important improvements in diabetes and cardiovascular indexes. For better credibility, the group convened in London was composed of a majority (75%) of non-surgeons, including endocrinologists, clinical practitioners, gastroenterologists, diabetologists and physiology researchers. They analyzed the data and concluded that it provides sufficient evidence that the mechanisms triggered by bariatric surgery – including changes in hormonal function, gut microbiota and insulin resistance – have a direct effect on metabolism. “The surgery usually results in weight loss, and we welcome that, but diabetes relapse does not appear to depend directly on this,” says Cohen.
In Brazil, the classification system proposed for evaluating the benefits of the surgery would be based on a metabolic risk score, determined through a patient evaluation questionnaire. “The systems proposed in other countries are similar,” says Cohen. He was awaiting publication of the DSS-II guidelines, endorsed by 46 medical societies worldwide, to support his arguments before the Federal Council of Medicine (CFM) requesting that metabolic surgery be regulated in Brazil.
The arguments are strong, but there is no consensus. According to endocrinologist Bruno Geloneze from the University of Campinas (Unicamp), there is no such thing as a purely metabolic surgery. “The metabolic impact of the surgery is due largely to weight loss,” he contends. “A patient with a lower BMI could have diabetes, but the lower the BMI, the lower the chances of a good outcome [against the disease].” He believes that gastric bypass surgery may not be worth it in these cases.
The procedure in itself is currently considered safe and can be performed via laparoscopy, with a low rate of complications during and immediately after surgery. But a post-surgical or clinical evaluation may not correspond to the patient’s everyday reality – they will need to change their diet and may no longer be able to eat certain types of food, or any type of food in large quantities. Gut-busting feasts on weekends and holidays become a thing of the past. “Whether it is worth it or not depends on a thorough examination of the potential long term benefits versus any complications that might occur, including malnutrition, fractures due to osteoporosis, and suicide, among others,” says the physician from Unicamp.
Geloneze’s research group performed clinical tests on non-obese patients, having them undergo a metabolic surgery model developed by surgeon Francesco Rubino from King’s College London, in England (who is also the first author of the DSS-II guidelines article). The procedure simply shifts a portion of the intestine, without reducing the stomach, and therefore does not lead to weight loss. “A year later, the patients had reduced their intake of insulin,” he says about the results, published in 2012 in the Annals of Surgery. The researchers at Unicamp are now preparing the five-year follow-up report. Geloneze says up front: the improvement was not permanent. He considers the results unsatisfactory. “It is a chronic disease. The effect of the treatment must also be chronic.”
For people with mild, or class I obesity (BMI of 30 to 35 kg/m2), he agrees that the surgery is effective in reducing hypertension, diabetes and other metabolic problems. Weight loss has the same effects, and so he insists on calling it bariatric surgery. A study involving 36 mildly obese patients who underwent what is known as a Roux-en-Y bypass (see infographic) showed improvements in every metabolic index within the first year, according to an article published in 2015 in Obesity Surgery. Two years later, weight and blood sugar were still well-controlled and diabetes indexes were probably better than would have been achieved with a purely clinical treatment. But for most patients, especially those who had lived with diabetes for longer periods, the disease could not be considered cured or in remission. “When we look at 25% or 30% reversal rates, we need to discuss whether the risks of the surgery are worth it on a case-by-case basis,” says Geloneze.
The differences of opinion seem more deeply rooted in the focus of each researcher’s work than on their results per se. As a researcher and clinical practitioner, Geloneze aims to understand the mechanisms by which the surgery affects metabolic function. His view agrees with the considerations published by the DSS-II, which emphasize the need for research that explains the functional roles of the different parts of the intestine in the development and treatment of diabetes. While this knowledge remains undiscovered, the priority of the experts convened in London is to ensure access to surgery (including by means of regulations allowing coverage by healthcare plans) for patients who are not morbidly obese and who are unable to control their diabetes through medication alone. The minimum required BMI would be 30 kg/m2 for much of the world and a bit less for Asians, whose diabetes risk starts increasing significantly with lower levels of weight gain. “The drugs have improved, but it’s a wretched disease,” says Cohen.
And the threat is global. In 2015, the International Diabetes Federation estimated that about 415 million people were affected by the disease, with the potential to reach 642 million by 2040, according to a review prepared by Cohen’s research group and accepted for publication by the journal Arquivos Brasileiros de Cirurgia Digestiva. Brazil takes fourth place in that lethal ranking, with over 14 million known diabetics in 2015. Diabetes killed 5 million people worldwide in that same year: more than AIDS, tuberculosis and malaria combined.
With new lines of research, Geloneze is interested in alternatives to surgery, emphasizing some promising pharmacological developments that, in his opinion, may render the whole discussion anachronistic. In partnership with physician Licio Velloso, also from Unicamp, he intends to study changes in brown fat, a type of fatty tissue thought to be beneficial, in patients who have undergone bariatric surgery. “After surgery, GLP-1 production increases,” he says, referring to a molecule called glucagon-like peptide 1, which stimulates brown fatty tissue. According to Geloneze, brown fat increases the production of bile acids, which in turn are associated with weight loss and lowered blood sugar. He hopes that a better understanding of these mechanisms will shed light on new clinical methods that could eliminate the need for surgery.
RUBINO, F. et al. Metabolic surgery in the treatment algorithm for type 2 diabetes: A joint statement by international diabetes organizations. Diabetes Care. Vol. 39, No. 6, pp. 861-77. Jun. 2016.
COHEN, R. V. et al. Effects of gastric bypass surgery in patients with type 2 diabetes and only mild obesity. Diabetes Care. Vol. 35, No. 7, pp. 1420-8. Jul. 2012.
FELLICI, A. C. et al. Surgical treatment of type 2 diabetes in subjects with mild obesity: Mechanisms underlying metabolic improvements. Obesity Surgery. Vol. 25, No. 1, pp. 36-44. Jan. 2015.
GELONEZE, B. et al. Metabolic surgery for non-obese type 2 diabetes: incretines, adipocytokines, and insulin secretion/resistance changes in a 1-year interventional clinical controlled study. Annals of Surgery. V. 256, No. 1, pp. 72-8. Jul. 2012.
CAMPOS, J. et al. O papel da cirurgia metabólica para tratamento de pacientes com obesidade grau I e diabetes tipo 2 não controlados clinicamente. Arquivos Brasileiros de Cirurgia Digestiva. In press.