STOCKHOLM – Bariatric surgery must expand to larger numbers of severely obese patients with complicated disease, but be cautious in patients with a body mass index below 35 kg/m2 where surgery remains investigational, researchers advised in a presentation at the 11th International Congress on Obesity.
Bariatric surgery “should be the standard of care for patients with complex, morbid obesity, patients with a body mass index of 40 kg/m2 or greater with related diseases, including type 2 diabetes, that respond to weight loss,” said Dr. John B. Dixon, head of obesity research at Monash University in Melbourne. “At the moment we have patients with BMIs of 45 or 50 who we don’t treat with surgery; that’s a crisis.”
In most of the world, less than 1% of patients undergo bariatric surgery even when they meet current standards for performing surgery: a BMI of at least 40 kg/m2 or at least 35 kg/m2 plus comorbidity. In Australia, which has “one of the highest uptakes of bariatric surgery in the world,” and in the United States as well, use of bariatric surgery in these patients doesn’t crack 2% of the target population, even though bariatric surgery is now recognized as very effective and safe, he said. Patients with BMIs of more than 45 kg/m2 are “where lives are saved, people we can help now,” Dr. Dixon said.
Although Dr. Dixon has run studies that helped pioneer use of gastric banding in patients with BMIs of 30-35 kg/m2, he agrees with the statement earlier this year by the American Diabetes Association, which said there is “currently insufficient evidence to generally recommend surgery in patients with BMI of less than 35 kg/m2 outside of a research protocol” (Diabetes Care 2010;33:S11-S61).
“We need better quality evidence before lowering the threshold for bariatric-metabolic surgery for lower BMI. We will need properly conducted randomized controlled trials, and benefits are likely to be less substantial than in the severely obese” patients, he said.
Dr. Dixon and his associates published in 2006 results from a study that randomized 80 patients with BMIs of 30-35 kg/m2 and no comorbidities to gastric banding or a very low calorie diet, pharmacotherapy, and lifestyle change. After 2 years of follow-up, the surgery patients showed significantly better weight loss, resolution of metabolic syndrome, and quality of life (Ann. Intern. Med. 2006;144:625-33).
A second study reported 2 years later ran a similar design in 60 obese patients with type 2 diabetes and a BMI between 30 and 40 kg/m2. Gastric banding led to a 73% remission rate of type 2 diabetes during 2-year follow-up compared with a 13% remission rate in control patients managed by lifestyle changes only (JAMA 2008;299:316-23).
Outcomes like these have led to modest uptake of bariatric surgery in patients with BMIs less than 35 kg/m2, although generally no lower than a BMI of 33 kg/m2, Dr. Dixon said.
“What we see in Australia is that patients who are approaching a BMI of 35 and have trouble controlling their weight and have type 2 diabetes are receiving surgery, about 95% by gastric banding,” he said in an interview. Some Australian surgeons are clearing interested patients for the procedure if they have a current BMI of 33 or 34 kg/m2. But surgery cases with a BMI as low as 31 or 32 kg/m2 “are extraordinary,” he added.
A concern at lower BMI is that the risk-benefit balance in favor of surgery shifts and makes surgery a somewhat less attractive option. “At a BMI of 31 kg/m2 surgery may not be as good as when patients are bigger,” he said.
Medical coverage also helps determine the BMI when Australian patients undergo surgery. Public insurers and hospitals Down Under often balk at surgery even when a patient’s BMI is greater than 40 kg/m2, Dr. Dixon said, and publicly-funded surgery in patients with BMIs below 35 kg/m2 does not happen. Bariatric surgery on patients with a BMI less than 35 kg/m2 needs private insurance, Dr. Dixon said.
Dr. Dixon said that he has served on speakers bureaus for Abbott, Bariatric Advantage, Eli Lilly, Merck, and Nestl? Australia; he has been a consultant to Allergan, Bariatric Advantage, Nestle Australia, Scientific Intake, and SP Health; and has received research support from Allergan, Nestl? Australia, ResMed, and Scientific Intake.