Bariatric surgery (or weight loss surgery) includes a variety of procedures performed on people who are obese. Long term weight loss through standard of care procedures (Roux en-Y bypass, sleeve gastrectomy, and biliopancreatic diversion with duodenal switch) is largely achieved by altering gut hormone levels that are responsible for hunger and satiety, leading to a new hormonal weight set point. Bariatric surgery is a hormonal surgery in these procedures, for which the alteration in gut hormones develops as a result of the procedure’s restriction and malabsorption.
Long-term studies show the procedures cause significant long-term loss of weight, recovery from diabetes, improvement in cardiovascular risk factors, and a mortality reduction from 40% to 23%. The U.S. National Institutes of Health recommends bariatric surgery for obese people with a body mass index (BMI) of at least 40, and for people with BMI of at least 35 and serious coexisting medical conditions such as diabetes. However, research is emerging that suggests bariatric surgery could be appropriate for those with a BMI of 35 to 40 with no comorbidities or a BMI of 30 to 35 with significant comorbidities. The most recent American Society for Metabolic & Bariatric Surgery guidelines suggest the position statement on consensus for BMI as an indication for bariatric surgery. The recent guidelines suggest that any patient with a BMI of more than 30 with comorbidities is a candidate for bariatric surgery.
A National Institute of Health symposium held in 2013 that summarized available evidence found a 29% mortality reduction, a 10-year remission rate of type 2 diabetes of 36%, fewer cardiovascular events, and a lower rate of diabetes-related complications in a long-term, non-randomized, matched intervention 15–20 year follow-up study, the Swedish Obese Subjects Study. The symposium also found similar results from a Utah study using more modern gastric bypass techniques, though the follow-up periods of the Utah studies are only up to seven years. While randomized controlled trials of bariatric surgery exist, they are limited by short follow-up periods.