Use of bariatric surgery for severe obesity has increased dramatically.

To systematically review 1. the clinical efficacy and safety, 2. cost-effectiveness of bariatric surgery, and 3. the association between number of surgeries performed (surgical volume) and outcomes.

MEDLINE (from 1950), EMBASE (from 1980), CENTRAL, EconLit, EURON EED, Harvard Center for Risk Analysis, trial registries and HTA websites were searched to January 2011.

1. Randomized controlled trials (RCTs) and 2. cost-utility and cost-minimisation studies comparing a contemporary bariatric surgery (i.e., adjustable gastric banding, Roux-en-Y gastric bypass, sleeve gastrectomy) to another contemporary surgical comparator or a non-surgical treatment or 3. Any study reporting the association between surgical volume and outcome.

Outcomes included changes in weight and obesity-related comorbidity, quality of life and mortality, surgical complications, resource utilization, and incremental cost-utility.

RCT data evaluating mortality and obesity-related comorbidity endpoints were lacking. A small RCT of 16 patients reported that adjustable gastric banding reduced weight by 27% (p < 0.01) compared to diet-treated controls over 40 weeks. Six small RCTs reported comparisons of commonly used, contemporary procedures. Gastric banding reduced weight to a lower extent than gastric bypass and sleeve gastrectomy and resulted in shorter operating times, fewer serious complications, lower weight loss efficacy, and more frequent reoperations compared to gastric bypass. Sleeve gastrectomy and gastric bypass reduced weight to a similar extent. A 2-year RCT in 50 adolescents reported that gastric banding substantially reduced weight compared to lifestyle modification (35 kg vs. 3 kg; p <0.001). Based on findings of 14 observational studies, higher volume centers and surgeons had lower mortality and complication rates. Surgery resulted in long-term incremental cost–utility ratios of $ <1.000–$ <1.000–40,000 (2009 USD) per quality-adjusted-life-year compared with non-surgical treatment.

Contemporary bariatric surgery appears to result in sustained weight reduction with acceptable costs but rigorous, longer-term (≥5 year) data are needed and a paucity of RCT data on mortality and obesity related comorbidity is evident. Procedure-specific variations in efficacy and risks exist and require further study to clarify the specific indications for and advantages of different procedures.