Metabolic surgery for the treatment of type 2 diabetes in patients with BMI lower than 35 kg/m²: Why caution is still needed

Abstract

Summary Bariatric surgery has shifted from being a risky procedure to an evidence‐based one, with proven benefits on all‐cause mortality, cardiovascular disease, cancer, and diabetes control. The procedure has an overall positive result on type 2 diabetes mellitus (T2DM), with a substantial number of patients achieving disease remission. This has resulted in several studies assessing possible weight‐independent effects of bariatric surgery on glycemic improvement, in addition to recommendation of the procedure to patients with class 1 obesity and T2DM, for whom the procedure was classically not indicated, and adoption of a new term, “metabolic surgery,” to highlight the overall metabolic benefit of the procedure beyond weight loss. Recently, the Diabetes Surgery Summit (DSS) has included metabolic surgery in its T2DM treatment algorithm. Although the discussion brought by this consensus is highly relevant, the recommendation of metabolic surgery for patients with uncontrolled T2DM and a body mass index of 30 to 35 kg/m2 still lacks enough evidence. This article provides an overall view of the metabolic benefits of bariatric/metabolic surgery in patients with class 1 obesity, compares the procedure against clinical treatment, and presents our rationale for defending caution on recommending the procedure to less obese individuals.

Type 2 diabetes and metabolic surgery guidelines and recommendations should urgently be unified

“…Many of these criteria are associated with worse glycemic outcomes in the long term (higher HbA1c, longer diabetes duration, and insulin use, for example) [17]. Very limited data regarding long-term reduced micro-and macrovascular risk exist in those patients with a longer diabetes duration.…”

“…In the body of the text, there is a mention that surgery may be considered for those patients between 30 and 35 kg/m 2 , in the same situation. In this guideline, differently from the DSS-II, the indication for class I obesity does not rely on glycemic control itself, but on weight loss and comorbidities, which seems more in line with the evidence [17]. Even so, diabetes duration, probably the most important factor regarding glycemic benefits, was omitted once again.…”

“…On the one hand, many physicians who treat patients with diabetes have very little knowledge about bariatric surgery, the different procedures, long-term outcomes, and complications, and do not discuss seriously and profoundly this option with their patients [15]. On the other hand, many surgeons have little knowledge of the pathophysiology of T2D and clinical trials with pharmacotherapy, and this could lead to an indication of surgery for patients whose benefits would be limited [16,17]. This gap between endocrinologists and surgeons is easily perceivable in guidelines and other joint statements [13,14,18,19].…”

Bariatric and metabolic surgery during and after the COVID-19 pandemic

“…Although many good-quality observational data suggest that cardiovascular disease risk and mortality are reduced after bariatric and metabolic surgery, the number of patients evaluated that already had cardiovascular disease is very small, and even smaller if we consider those with type 2 diabetes. 2 In the large Swedish Obese Subjects study, although similar benefits were suggested, only 1·5% of patients had a history of cardiovascular disease, and only 21 patients with cardiovascular disease were submitted to surgery. 3 …”

“… 1 We congratulate the authors for bringing up this important discussion, since difficulties around future care of obesity and type 2 diabetes might be a major problem within this context.We would like to point out, however, our disagreement with the algorithm for prioritisation for bariatric and metabolic surgery in patients with type 2 diabetes. Many diabetes characteristics the authors suggest be prioritised are associated with reduced long-term benefits (which we previously discussed in a review 2 ), but we would like to focus on one point here: established cardiovascular disease. This suggestion goes against current evidence.…”