Although multiple international medical societies over recent years have recommended lowering the threshold for bariatric surgery to a body mass index (BMI) of 30-35 (class 1 obesity) in certain patients (see box), very few patients in this weight category have had such surgery, according to a new study.
On the basis of data from a large US national registry, during 2015 through 2021, just 3.5% of metabolic and bariatric surgeries were performed in patients with class 1 obesity each year.
Most surgeries (96.5%) were in patients with a BMI > 35. This reflects advice from a 1991 consensus statement by the National Institutes of Health (NIH) stating that bariatric surgery can be offered to patients with BMI ≥ 40, or ≥ 35 with comorbidities.
However, medical societies have recommended lower cutoffs in position statements in 2016, 2018, and 2022 (see box).
Societies Call for Lower BMI Thresholds
Providers, hospitals, and insurers currently use BMI thresholds ≥ 40, or ≥ 35 with an obesity-related comorbidity, to define patients eligible for metabolic and bariatric surgery, based on criteria established in a 1991 consensus statement by NIH.
As more data accumulated, in 2016, a position statement from 45 societies recommended that bariatric surgery should be “considered for patients with [type 2 diabetes] and BMI 30.0-34.9 kg/m2 if hyperglycemia is inadequately controlled” despite optimal medical treatment.
Similarly, in 2018, the ASMBS issued a position statement saying that “for patients with BMI 30 to 35 kg/m2 and obesity-related co-morbidities who do not achieve substantial, durable weight loss and co-morbidity improvement with reasonable nonsurgical methods, bariatric surgery should be offered” to suitable individuals.
Then in October 2022, the ASMBS and International Federation for the Surgery of Obesity and Metabolic Disorders issued a joint statement that recommended lowering the thresholds for bariatric surgery to a BMI ≥ 35, or ≥ 30 with weight-related comorbidities, as reported by Medscape Medical News.
Paul Wisniowski, MD, a surgical resident at Keck School of Medicine of University of Southern California (USC), Los Angeles, presented the study findings in an e-poster at the American Society for Metabolic and Bariatric Surgery (ASMBS) 2023 annual meeting.
“Professional guidelines and increasing data support bariatric surgery for patients beginning at BMI 30, which is a tipping point for disease progression. Now it needs to happen in the real world,” outgoing ASMBS president Teresa LaMasters, MD, who was not involved with this research, said in an ASMBS press release.
“We encourage greater consideration of this important treatment option earlier in the disease process,” stressed LaMasters, a bariatric surgeon and Medical Director, Unity Point Clinic Weight Loss Specialists, West Des Moines, Iowa.
‘Not Unexpected,’ ‘Need to Expand Eligibility’
“We expected that there had been little widespread adoption of the new BMI criteria/cutoffs,” senior study author Matthew J. Martin, MD, told Medscape Medical News in an email.
“We know that bariatric surgery is already underutilized, as only about 1% to 2% of eligible patients who would benefit end up getting surgery,” added Martin, Chief, Emergency General Surgery, and Director, Acute Care Surgery Research, USC Medical Center and Keck School of Medicine.
He suggests that the main reason that more patients with lower BMIs are not being offered surgery is related to insurance coverage and reimbursement.
“Even though the professional society guidelines have changed, based on the scientific evidence, most insurers are still using the very outdated (1990s) NIH consensus criteria of BMI > 35 with comorbidities, or BMI > 40.”
Another potential reason is “the lack of awareness of the changing guidelines and recommendation among primary care physicians who refer patients for a bariatric surgery evaluation.”
“I think it is too early in the experience with the new, more effective antiobesity medications to say which group will benefit the most or will prefer them over surgery,” he said.
“There is still only a small minority of patients who end up getting the [newer antiobesity] medications or surgery.”
“The takeaway,” Martin summarized, “is that bariatric surgery remains the only intervention with a high success rate for patients with class 1 or higher obesity in terms of weight loss, comorbidity improvement or resolution, and sustained health benefits.”
“We need to expand the availability of bariatric surgery for all eligible patients, and particularly the class 1 obesity population who are currently the most underserved,” he said.
“This will take continued lobbying and working with the insurance companies to update their guidelines/criteria, education of patients, and education of primary care physicians so that patients can be appropriately referred for a surgical evaluation.”
Surgery vs Pharmacotherapy
Invited to comment on this study, Neil Skolnik, MD, who was not involved with this research, noted that data from patients with a lower BMI “has continued to accumulate, showing much greater safety than earlier studies, and giving further support of efficacy.”
However, “[new] recommendations take time to take hold,” noted Skolnik, a family physician and professor in the Department of Family Medicine, Thomas Jefferson University, Philadelphia.
“And from March of 2020 through 2021, surgery referrals were likely influenced by the COVID pandemic,” he added in an email.
Skolnik authored a commentary on Medscape sharing his reservations about ASMBS recommendations issued in 2022 for lower BMI thresholds for this surgery.
“Medications are a safe, effective option for patients with a BMI from 30 to 35,” he said, “and [they] achieve approximately a 15% to 20% average weight loss, which is enough to markedly improved both metabolic parameters and biomechanical issues such as knee pain, hip pain and back pain.”
However, “bariatric surgery remains an excellent option for patients who do not respond sufficiently to pharmacotherapy,” he acknowledged.
National Registry Study, 2015-2021
Wisniowski and colleagues analyzed data from around 900 US centers that are currently part of the Metabolic Bariatric Surgery Accreditation Quality Improvement Program.
They found that during 2015 to 2021, 38,669 patients (3.5%) with type 1 obesity and 1,1067,094 patients (96.5%) with a higher BMI had metabolic and bariatric surgery.
Compared with patients with BMI > 35, those with class 1 obesity had shorter operating times and hospital stays, but they lost less weight on short-term evaluation, after multivariable adjustment.
There were no significant differences between the two patient groups in rates of postoperative complications (< 5%) or mortality (< 0.1%).
Sleeve gastrectomy was the most common procedure and increased from 70% to 76% of all procedures during the study period.
Single-Center Study
In a second e-poster presented at the meeting, Tina T. Thomas, MD, New Jersey Bariatric Center, analyzed data from 23 patients with BMI < 35 or < 30 with comorbidities who had sleeve gastrectomy or Roux-en-Y gastric bypass at their center during 2017 to 2021 and who had 6 months of follow-up data.
At study entry, the patients had a mean BMI of 33.5. At 6 months after the surgery, they had a mean BMI of 25.6, and on average, they had lost 55% of their excess weight.
Nearly 60% of the patients had lost at least 50% of their excess weight, and nine of 16 patients (56%) with comorbidities had improved or resolved comorbidities. None of the patients died or had surgery-related complications.
“Our study shows significant weight loss and health benefits, as well as the safety and efficacy of the gastric bypass and gastric sleeve procedures, for this patient population,” Ajay Goyal, MD, senior author, and bariatric surgeon at New Jersey Bariatric Center, said in an ASMBS press release.
“Often by the time a patient qualifies for bariatric surgery their weight-related medical conditions such as [type 2] diabetes and hypertension are severe. By expanding access to bariatric surgery to patients with a lower BMI with obesity-related illnesses, patients can halt the progression, and in some cases resolve, significant and uncontrolled weight-related chronic diseases through weight loss.”
ASMBS 2023 Annual Meeting. Abstract A167; Abstract A214.
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