Cochrane Summaries

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Surgery for obesity Updated

Colquitt JL, Pickett K, Loveman E, Frampton GK
Published Online: 
8 August 2014

Review question

What are the effects of weight loss (bariatric) surgery for overweight or obese adults?


Obesity is associated with many health problems and a higher risk of death. Bariatric surgery for obesity is usually only considered when other treatments have failed. We aimed to compare surgical interventions with non-surgical interventions for obesity (such as drugs, diet and exercise) and to compare different surgical procedures. Bariatric surgery can be considered for people with a body mass index (BMI = kg/m²) greater than 40, or for those with a BMI less than 40 and obesity-related diseases such as diabetes.

Study characteristics

We included 22 studies, 1496 participants were allocated to surgery and 302 participants to non-surgical interventions. Most studies followed participants for 12 to 36 months, the longest follow-up was 10 years. The majority of participants were women and, on average, in their early 30s to early 50s.

Key results

Seven studies compared surgery with non-surgical interventions. One to two years following surgery, BMI was on average 6 units lower than in people who did not have surgery. Improvements in quality of life and diabetes were also found. No deaths occurred, reoperations in the surgical intervention groups ranged between 2% and 13%.

Three studies found that gastric bypass achieved greater weight loss up to five years after surgery compared with adjustable gastric band: the BMI at the end of the studies was on average five units less. The gastric bypass procedure resulted in greater duration of hospitalisation and a greater number of late major complications. Adjustable gastric band required high rates of reoperation for removal of the gastric band.

Seven studies compared gastric bypass with sleeve gastrectomy. Overall there were no important differences for weight loss, quality of life, comorbidities and complications, although gastro-oesophageal reflux disease improved in more patients following gastric bypass in one study. One death occurred in the gastric bypass group. Serious adverse events occurred in 5% of the gastric bypass group and 1% of sleeve gastrectomy group, as reported in one study. Two studies reported 7% to 24% of people with gastric bypass and 3% to 34% of those with sleeve gastrectomy requiring reoperations.

Two studies found that biliopancreatic diversion with duodenal switch resulted in greater weight loss than gastric bypass after two or four years in people with a relatively high BMI, BMI was on average seven units lower. One death occurred in the biliopancreatic diversion group. Reoperations were higher in the biliopancreatic diversion group (16% to 28%) than the gastric bypass group (4% to 8%).

One study comparing duodenojejunal bypass with sleeve gastrectomy versus gastric bypass found weight loss outcomes and rates of remission of diabetes and hypertension were similar at 12 months follow-up. No deaths occurred in either group, reoperation rates were not reported.

One study found that BMI was reduced by 10 units more following sleeve gastrectomy at three years follow-up compared with adjustable gastric band. Reoperations occurred in 20% of the adjustable gastric band group and in 10% of the sleeve gastrectomy group.

One study found no relevant difference in weight-loss outcomes following gastric imbrication compared with sleeve gastrectomy. No deaths occurred; 17% of participants in the gastric imbrication group required reoperation.

Quality of the evidence

We found that surgery resulted in greater improvement in weight-loss outcomes and some weight associated comorbidities compared with non-surgical interventions, regardless of the type of procedure used. When compared with each other, certain procedures resulted in better weight-loss outcomes than others, but not all procedures were compared with each other and some were only carried out in people with relatively low or relatively high BMI. Adverse events were not consistently reported in the publications of the studies. Most studies followed participants for only one or two years, therefore the long-term effects of surgery remain unclear.

Few studies assessed the effects of bariatric surgery in treating comorbidities in participants with a lower BMI. There is therefore a lack of evidence for the use of bariatric surgery in treating comorbidities in people who are overweight or who do not meet standard criteria for bariatric surgery.

Currentness of data

This evidence is up to date as of November 2013.

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