October 16, 2019
5 min read

Experts urge lower BMI cutoff for bariatric surgery

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Bariatric surgery is an aggressive therapeutic strategy for weight loss that can also yield many other health benefits, but this option has been restricted to adolescents and adults with a BMI of at least 35 kg/m2 if they have obesity-related comorbidities or 40 kg/m2 if they have no other health problems. That BMI limitation may be changing as research points to advantages of a lower cutoff.

Ali Aminian

“The existing BMI cut point of 35 kg/m2 for considering bariatric surgery is an arbitrary cut point without strong scientific background,” Ali Aminian, MD, FACS, FASMBS, associate professor of surgery at the Cleveland Clinic, told Endocrine Today. “BMI alone is a poor indicator of cardiovascular and metabolic risk.”

The benefits of bariatric surgical procedures begin with substantial reductions in weight, ranging from 15% to 35%, according to Scott Kahan, MD, MPH, director of the National Center for Weight and Wellness, and a faculty member of the Johns Hopkins Bloomberg School of Public Health and the George Washington University Milken Institute for Public Health. Kahan, who is also an Endocrine Today Editorial Board Member, noted that bariatric surgery can also reduce or eliminate hypertension, hyperlipidemia, sleep apnea and diabetes. Bariatric surgery may lead to lower medication costs as well.

The potential for diabetes remission is a key reason to lower the BMI threshold for bariatric surgery, according to Kahan.

Scott Kahan

“The main consideration of the possibility of surgery in people with lower BMI is when they have difficult-to-treat diabetes,” Kahan told Endocrine Today. “There seems to be a metabolic benefit of bariatric surgery that is separate from the weight-loss benefit. ... Even before [people with diabetes] lose weight, they tend to get very impressive improvements in their diabetes in that time, even with relatively small weight losses.”

The underlying mechanism behind bariatric surgery’s benefits outside of weight loss is how this treatment “changes the physiology of the control of body weight,” according to Frank Greenway, MD, professor and chief medical officer at the Pennington Biomedical Research Center of Louisiana State University. These changes help patients combat weight regain more effectively than diet and exercise alone, which can lead to additional benefits outside of weight reduction.

“Obesity is physiologically controlled like blood pressure or blood sugar. If one loses weight by changing their lifestyle — exercising regularly and reducing food intake — weight regain is the rule, not the exception,” Greenway told Endocrine Today. “It is possible to overcome physiology with behavior for a period of time, but when other life stresses compete with maintaining a diet and exercise program, the stress usually wins and weight returns, because the physiology is programed to return weight to the preweight loss level.”


‘Off-label’ unlikely

Despite a growing body of recent research suggesting that bariatric surgery can be safe and effective for patients with a lower BMI, guidelines still dictate that procedures be offered only to those with a BMI of at least 35 kg/m2. The guidelines as set by professional organizations, such as the American Society for Metabolic and Bariatric Surgery (ASMBS), are what drive decisions by surgeons and health insurance companies. Until guidelines change, insurance companies will likely not cover patients with a lower BMI, creating a financial barrier for these individuals. This cutoff not only limits who can receive the surgeries, but who will perform them, according to Greenway.

Frank Greenway

“If one goes outside the package insert recommendations, one usually discusses it with the patient and prescribes off-label under exceptional circumstances that can be justified, often with the patient giving written consent,” Greenway said. “This is similar with surgery. If something were to happen and a legal challenge resulted, this sort of documentation and agreement to do something outside the guidelines would be important. Due to the cost of surgery, the lack of reimbursement outside the guidelines puts an additional restraint on using surgery outside the guidelines than is the case with medications.”

Weight-loss therapies besides surgery are available to people with a lower BMI. In addition to increasing exercise and decreasing caloric intake, there are medications, minimally invasive medical devices, the recently approved oral hydrogel capsule and weight-loss supplements. However, there are drawbacks to these alternative aids, according to Kahan.

“There are going to be some or many that don’t respond to these treatments or don’t get enough benefit,” Kahan said. “Having options for treatment escalation, in this case with bariatric surgery, can be very valuable in many people who need it.”

Operating room surgery 
The BMI limitation for bariatric surgery may be changing as research points to advantages of a lower cutoff.
Source: Adobe Stock

Changing the guidelines

Although the guideline changes needed to open bariatric surgery to more patients have not been made, the possibility is increasing. In a position statement released in August 2018, ASMBS revised its recommendation from 2012 and urged the consideration of the use of bariatric surgery for individuals with a BMI between 30 kg/m2 and 35 kg/m2. The International Federation for the Surgery of Obesity and Metabolic Disorders also endorses this lower cutoff, according to the position statement.

“Having new consensus guidelines that become widely adopted, as were the guidelines that arose from the 1991 NIH consensus conference, is the first step in amending the criteria for insurance coverage of the obesity operation,” Greenway said, noting that these guidelines would not need to be accepted by insurance companies before more access could be achieved.


“Even having a change in the guidelines before adoption by insurance could result in an expansion of the procedures, since many of the procedures not covered by insurance are done through cash payment with arrangements for financing,” Greenway said. “Many surgeons are understandably unwilling to do surgical procedures for obesity outside the guidelines, but once the guidelines were amended, the new indications would be more likely to be followed in the surgeries that were financed through a lender rather than the traditional medical insurance mechanism.”

Caroline M. Apovian

Of course, getting insurance companies onboard would be a critical step to ensuring that bariatric surgery is more readily available to anyone who might need it.

“Insurance companies typically look to guidelines developed by professional societies as part of their criteria for determining eligibility for procedures and coverage for procedures, so if ASMBS and or other professional societies were to change their recommendations and criteria for bariatric surgery, then many of the insurers would certainly consider those changes in their own benefit plans,” Kahan said.

It is also possible that BMI cutoffs alone should not be the primary consideration when determining therapeutic options for weight loss, according to Caroline M. Apovian, MD, director of Nutrition and Weight Management, professor of medicine at the Boston University School of Medicine and an Endocrine Today Editorial Board Member.


ASMBS. ASMBS updated position statement on bariatric surgery in class I obesity. Available at: https://asmbs.org/resources/asmbs-updated-position-statement-on-bariatric-surgery-in-class-i-obesity.

For more information:

Ali Aminian, MD, FACS, FASMBS, can be reached at AMINIAA@ccf.org.

Caroline M. Apovian, MD , can be reached at Caroline.Apovian@bmc.org.

Frank Greenway, MD, can be reached at Frank.Greenway@pbrc.edu.

Scott Kahan, MD, MPH, can be reached at kahan@gwu.edu.

Disclosures: Aminian and Kahan report no relevant financial disclosures. Apovian reports she is on the scientific advisory board of Novo Nordisk Janssen. Greenway reports he is on the scientific advisory board for Gelesis, Jenny Craig-Curves, Microbiome Therapeutics, NuSirt Sciences, PlenSat, Regeneron Pharmaceuticals and Zafgen; a consultant to Basic Research Corp. and General Nutrition Corp.; has a patent application with Melior Discovery and patents licensed to NeuroQuest and Slim Health Nutrition; is a partner in Academic Technology Ventures and part owner of Nutricado and Slim Health Nutrition; has stock or stock options in Microbiome Therapeutics, PlenSat and Zafgen; and has received grants through his institution from Lilly Pharmaceuticals, Novartis Pharmaceuticals, Novo Nordisk Pharmaceuticals and Vivus Pharmaceuticals.