Bariatric Surgery and Nonsurgical Therapy in Adults with Metabolic Conditions and a Body Mass Index of 30.0 to 34.9 Kg/M²

OBJECTIVES: To systematically review the scientific evidence on efficacy, safety, and comparative effectiveness of various types of bariatric surgery for treating adult patients with a body mass index (BMI) of 30.0 to 34.9 kg/m² and diabetes or impaired glucose tolerance (IGT) and to compare effectiveness of surgery versus nonsurgical interventions in this population. DATA SOURCES: Systematic reviews, case series, cohort, case control studies and controlled trials, found through searching PubMed®, Embase, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Database of Abstracts of Reviews of Effects (DARE), and Clinicaltrials.gov through March, 2012. REVIEW METHODS: To be included, studies had to report on laparoscopic adjustable gastric banding (LAGB), Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion with duodenal switch (BPD), sleeve gastrectomy (SG), or nonsurgical treatment, and had to include patients with a BMI of at least 30 kg/m2 but less than 35 kg/m² with diabetes or IGT. The following studies were excluded: (1) those with no outcomes of efficacy, effectiveness, or safety/adverse events; (2) nonsurgical studies with less than one year followup; (3) nonsurgical studies already included in previous systematic reviews; and (4) studies with a sample size of less than three. Two reviewers, each trained in the critical analysis of scientific literature, independently reviewed and abstracted each study. RESULTS: We found only 24 studies reporting bariatric surgery results in this specific target population. Two were trials comparing different procedures, three were trials of surgical versus nonsurgical interventions, and the rest were observational studies. Both weight and blood glucose improved significantly for surgery patients in the trials. In the observational studies, surgery patients showed much greater weight loss at 1 year than reported in systematic reviews and randomized controlled trials (RCTs) on diet, exercise, medication, and other behavioral interventions. While both behavioral interventions and medications lowered HbA1c (glycosylated hemoglobin) levels significantly, the decreases reported in surgery patients were much greater. Improvements in blood glucose measures were reported as early as one month postsurgery. Improvements in hypertension, low-density lipoprotein (LDL) cholesterol, and triglycerides were also reported in some studies. Short-term rates of adverse events associated with bariatric surgery were relatively low. One death, a case of sepsis at 20 months in an LAGB patient, was reported. Short-term complications were minor and tended not to require major intervention. Due to the dearth of long-term studies of bariatric surgery in this particular target population, few data exist about long-term adverse effects, and we found no evidence regarding major clinical endpoints such as all-cause mortality, cardiovascular mortality and morbidity, and peripheral arterial disease. CONCLUSIONS: According to blood glucose outcomes, there is moderate strength evidence of efficacy for RYGB, LAGB, and SG as treatment for diabetes and IGT in patients with a BMI ix between 30 kg/m2 and 35 kg/m2 in the short term (up to 2 years). The strength of evidence for BPD is rated low because there are fewer studies, and these have smaller sample sizes. Evidence on comparative effectiveness of surgical procedures is insufficient. Short-term adverse events are relatively minor; strength of evidence is low due to small sample size with low power to detect rare events. Strength of evidence is insufficient regarding adverse events in the long-term (2 years or more postsurgery). Longitudinal studies of bariatric surgery patients are needed to assess overall safety and comparative effectiveness regarding diabetes-related morbidity such as kidney failure and blindness.