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Bariatric surgery shows metabolic benefits in lower-BMI patients

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Findings add to a growing evidence base

This is a very important topic and study, and its findings are very positive and reinforcing for more liberal use of bariatric surgery. Results from several prior studies had documented the safety and efficacy of bariatric surgery in patients with lower body mass index, and its fantastic to now have additional data that show the same outcomes. A major challenge is making patients and more physicians aware of the range of comorbidities that can be effectively managed with bariatric surgery, even in patients with lower body mass index.

Dr. Mona Misra, bariatric surgeon, Cedars-Sinai Marina Del Rey Hospital, Los Angeles

Dr. Mona Misra

Mona Misra, MD, is associate director of the Bariatric Program at Cedars-Sinai Marina Del Rey Hospital in Los Angeles. She had no relevant disclosures. She made these comments as designated discussant for the study.



– It’s time to take bariatric out of bariatric surgery.

“The way forward is to not call it bariatric surgery or weight-loss surgery but surgery to treat diabetes, hypertension, hyperlipidemia, and other metabolic diseases,” said Oliver A. Varban, MD, at a meeting presented by the Obesity Society and the American Society for Metabolic and Bariatric Surgery. “We need to reframe the conversation with patients about what success [with bariatric surgery] looks like. Weight loss can be a side effect of the operation if patients have surgery to resolve their diabetes. It’s not about BMI; it’s about treating metabolic disease.”

Dr. Oliver A. Varban, bariatric surgeon, University of Michigan, Ann Arbor Mitchel L.Zoler/MDedge News

Dr. Oliver A. Varban

Dr. Varban, a bariatric surgeon at the University of Michigan in Ann Arbor, reported data showing that bariatric surgery with sleeve gastrectomy in patients with baseline body mass index (BMI) levels below 35 kg/m2 was as effective at normalizing a range of metabolically associated disorders as it was in more obese patients in an observational study of more than 45,000 patients who underwent surgery in Michigan.

The findings add to an already extensive pool of evidence for loosening current guidelines that restrict bariatric surgery to patients with a BMI of 35 kg/m2 or greater, Dr. Varban said. But an influential bariatric surgery consensus statement from the National Institutes of Health that dates from 1991 and remains in place, recommends this surgery only for people with a BMI of at least 35 kg/m2, and this guidance often limits access to the surgery for patients at lower BMI, he noted.

A more inclusive assessment of patients as potential candidates for bariatric surgery should include a range of considerations in addition to weight and height, he explained in an interview. “Even if people have a BMI of less than 30 kg/m2 but have, or are at high risk for developing, metabolic disease, they should also be offered the operation.”

The guidance from the NIH results in a U.S. bariatric surgery population that effectively centers mainly on women with a BMI of 40 kg/m2 or greater and makes procedures like sleeve gastrectomy unavailable to many other types of patients who could benefit from it, Dr. Varban said. In 2018, the American Society for Metabolic and Bariatric Surgery released a position statement that summarized the evidence for the safety and efficacy of bariatric surgery in people with a BMI of 30-34 kg/m2, and cited the lingering and restrictive impact of the 1991 NIH consensus statement.

The study run by Dr. Varban and his associates used data collected by 43 programs in the Michigan Bariatric Surgery Collaborative during 2006-2018 that included 1,073 patients who had a BMI of less than 35 kg/m2 on the day they underwent sleeve gastrectomy, and 44,511 patients who had the same procedure and had a BMI of at least 35 kg/m2. The operations were performed by any one of 81 surgeons who worked at the centers during this time.

The patients with lower BMIs were older, with an average age of 51 years, compared with 45 years in the higher-BMI group, and they had higher prevalences of certain metabolic disorders. Diabetes affected 37% of those in the lower-BMI group and 31% of those with higher BMIs; hyperlipidemia affected 57% and 45%, respectively; and gastroesophageal reflux disease affected 56% and 49%, respectively. Obstructive sleep apnea was more common in the group with higher BMIs, at 47%, compared with 41% of those with lower BMIs.

The average BMI in the lower group was 33.7 kg/m2; in the higher group it was 46.7 kg/m2. Dr. Varban did not have data on whether any patients in the lower-BMI group had a BMI below 30 kg/m2. Roughly a third of the patients in the lower-BMI group had a BMI of less than 35 kg/m2 at the time of their initial examination, whereas the other two-thirds had a BMI that low only on the day of their surgery.At follow-up 1 year after their surgery, patients who started with lower BMIs had, in general, a very similar pattern of responses as those who started with higher BMIs, with rates of discontinuation of treatments for diabetes, hypertension, hyperlipidemia, obstructive sleep apnea, and gastroesophageal reflux of about 50%-80% and similar in both treatment arms. For example, discontinuation of oral diabetes drugs occurred in 79% and 78% of those with low and high BMIs, respectively, and discontinuation of hypertension medications occurred in 60% and 54%, respectively. Although the average absolute weight loss in the patients with lower BMIs was nearly half that of patients with higher starting BMIs, a much greater percentage of patients in the lower-BMI group achieved a BMI of less than 25 kg/m2, compared with the higher-BMI group (36% vs. 6%, respectively).

Patients from the lower-BMI group also showed high levels of satisfaction with their surgery and its results after 1 year. Questionnaire results from roughly half the patients in each treatment group showed that 90% were very satisfied in the lower-BMI group, compared with 84% of those who began with higher BMIs, with a dissatisfaction rate of 1% and 2%, respectively. The average body-image score at 1 year follow-up was significantly higher in those who started with lower BMIs. The rate of complications was low and similar in the two groups, with a 6% rate in the lower-BMI group and 5% in those with higher BMIs.

The study received no commercial funding. Dr. Varban receives salary support from Blue Cross Blue Shield of Michigan.

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SOURCE: Varban et al. Obesity Week 2019, Abstract A105.

This article was updated 11/8/2020.

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