Bariatric/Metabolic Surgery to Treat Type 2 Diabetes in Patients With a BMI <35 kg/m2

Abstract

OBJECTIVE Global usage of bariatric surgery has been dictated for the past quarter century by National Institutes of Health recommendations restricting these operations to individuals with a BMI ≥35 kg/m2. Strong evidence now demonstrates that bariatric procedures markedly improve or cause remission of type 2 diabetes mellitus (T2DM), in part through weight-independent mechanisms, and that baseline BMI does not predict surgical benefits on glycemic or cardiovascular outcomes. This impels consideration of such operations as “metabolic surgery,” which is used expressly to treat T2DM, including among patients with a BMI &lt;35 kg/m2 who constitute the majority of people with diabetes worldwide. Here, we review available evidence to inform that consideration. RESULTS A meta-analysis of the 11 published randomized clinical trials (RCTs) directly comparing bariatric/metabolic surgery versus a variety of medical/lifestyle interventions for T2DM provides level 1A evidence that surgery is superior for T2DM remission, glycemic control, and HbA1c lowering. Importantly, this is equally true for patients whose baseline BMI is below or above 35 kg/m2. Similar conclusions derive from meta-analyses of high-quality nonrandomized prospective comparisons. Meta-analysis of all pertinent published studies indicates that T2DM remission rates following bariatric/metabolic surgery are comparable above and below the 35 kg/m2 BMI threshold. The safety, antidiabetes durability, and benefits on other cardiovascular risk factors from bariatric/metabolic surgery appear roughly comparable among patients with a BMI below or above 35 kg/m2. Further studies are needed to extend long-term findings and measure “hard” macrovascular/microvascular outcomes and mortality in RCTs. CONCLUSIONS Extant data, including level 1A evidence from numerous RCTs, support new guidelines from the 2nd Diabetes Surgery Summit that advocate for the consideration of bariatric/metabolic surgery as one option, along with lifestyle and medical therapy, to treat T2DM among patients with a BMI &lt;35 kg/m2.