Bariatric Surgery for Weight Loss and Glycemic Control in Nonmorbidly Obese Adults With Diabetes: A Systematic Review

Study Questions:

Is there an association between bariatric surgery versus nonsurgical treatments and weight loss and glycemic control among patients with diabetes or impaired glucose tolerance and body mass index (BMI) of 30-35 kg/m2?


PubMed, EMBASE, and Cochrane Library databases were searched from January 1985 through September 2012. Of 1,291 screened articles, 32 surgical studies, 11 systematic reviews on nonsurgical treatments, and 11 large nonsurgical studies published after those reviews were included. Weight loss, metabolic outcomes, and adverse events were abstracted by two independent reviewers.


Three randomized clinical trials (RCTs) (N = 290; including one trial of 150 patients with type 2 diabetes and mean BMI of 37, one trial of 80 patients without diabetes [38% with metabolic syndrome] and BMI of 30-35, and one trial of 60 patients with diabetes and BMI of 30-40 [13 patients with BMI <35]) found that surgery was associated with greater weight loss (range, 14.4-24 kg) and glycemic control (range, 0.9-1.43 point improvements in glycated hemoglobin levels) during 1-2 years of follow-up than nonsurgical treatment. Indirect comparisons of evidence from observational studies of bariatric procedures (600 patients) and meta-analyses of nonsurgical therapies (containing more than 300 RCTs) support this finding at 1 or 2 years of follow-up. However, there are no robust surgical data beyond 5 years of follow-up on outcomes of diabetes, glucose control, or macrovascular and microvascular outcomes. In contrast, some RCT data of nonsurgical therapies show benefits at 10 years of follow-up or more. Surgeon-reported adverse events were low (e.g., hospital deaths of 0.3%-1.0%), but data were from select centers and surgeons. Long-term adverse events are unknown.


Current evidence suggests that, when compared with nonsurgical treatments, bariatric surgical procedures in patients with a BMI of 30-35 and diabetes are associated with greater short-term weight loss and better intermediate glucose outcomes. Evidence is insufficient to reach conclusions about the appropriate use of bariatric surgery in this population until more data are available about long-term outcomes and complications of surgery.


The bar for bariatric surgery in obesity has been lowered to include BMI between 35 and 39.9, along with an obesity-related health problem such as type 2 diabetes, heart disease, or severe sleep apnea. The value in overweight and mildly obese persons (BMI 30 to <35) needs to be assessed in a clinical outcome trial.

Clinical Topics: Heart Failure and Cardiomyopathies, Sleep Apnea

Keywords: Heart Diseases, Hemoglobin A, Glycosylated, Bariatric Surgery, Body Mass Index, Weight Loss, Diabetes Mellitus, Type 2, Obesity, Sleep Apnea Syndromes

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