At larger institutions and accredited metabolic and bariatric surgery (MBS) programs, preoperative evaluations are often built into a comprehensive protocol. However, this is not always the case, as some components of the workup may be deferred to outside providers or primary care physicians. Regardless of your role or affiliation with an MBS program, the ABOM (and your patients in a weight management clinic) will expect you to understand the essential elements of the preoperative evaluation and recognize who qualifies as a good surgical candidate. Today’s blog is part one of a two-part series covering the preoperative assessment for patients undergoing MBS, based on the comprehensive 2019 guidelines from the ASMBS. In this post, we’ll focus on patient candidacy, while next week’s blog will explore the specifics of the preoperative workup, including lab testing, cardiac evaluation, and more.

In terms of eligibility, the updated ASMBS guidelines (2022, found here) broadened the criteria for who may qualify for MBS, reflecting the durable benefits of surgery and its impact on obesity-related comorbidities. The revised guidelines emphasized some key points and lowered the BMI indication thresholds:

  • BMI ≥30 kg/m² with metabolic disease (e.g., type 2 diabetes); BMI ≥27.5 kg/m² for individuals of Asian descent
  • BMI ≥35 kg/m² regardless of comorbidities
  • BMI ≥60 kg/m²: MBS can be safely performed in individuals with very high BMIs, including those exceeding 70 kg/m². Due to the high mortality associated with severe obesity, MBS should be considered the preferred intervention for achieving clinically meaningful weight loss in this population.
  • Older adults: There is no specific age cutoff; rather, frailty is a better predictor of complications than chronological age.
  • Pediatric and adolescent patients: Similarly, there is no age cutoff. According to the American Academy of Pediatrics, MBS should be offered at age 13 in cases of severe obesity. Tanner stage, pubertal status, and bone age should not be used to determine surgical candidacy.

Additionally, MBS serves as an effective bridge to other surgical procedures. For example, undergoing MBS before total knee arthroplasty has been shown to reduce orthopedic operative time, hospital length of stay, and postoperative complications. Similar benefits have been observed in patients undergoing MBS prior to abdominal hernia repair and organ transplantation.

In contrast, there are certain patients who may not be ideal candidates for MBS. Most of these concerns are considered transient or relative contraindications and can often be addressed or modified, as discussed below.

Pregnancy: Patients planning pregnancy within the next two years or not actively preventing pregnancy are not ideal candidates. Weight loss significantly increases fertility, and becoming pregnant within the first 12 months post-MBS carries a higher risk of complications. Additionally, it is recommended that oral estrogen-containing contraceptives should be discontinued one cycle prior to surgery (three weeks for hormonal replacement therapy) to reduce perioperative venous thromboembolism risk. Discontinuing oral contraception, however, does increase the chances of pregnancy pre-operatively, which should be considered.

Mental health: Uncontrolled eating disorders, active psychosis, severe depression, or suicidal ideation are contraindications to surgery. These conditions can impair adherence and worsen outcomes if not properly managed. There is no minimum time a patient must demonstrate stability, but ongoing engagement with mental health professionals is critical throughout the process.

Gastrointestinal disease: Conditions such as inflammatory bowel disease, active peptic ulcer disease, or GI motility disorders must be well-controlled before surgery. Surgeons may require additional diagnostics, such as endoscopy, to guide decision-making. Active GI inflammation at the time of surgery increases the risk for complications like ulceration, anastomotic leaks, and fistula formation.

Motivation: MBS requires significant behavioral, nutritional, and psychological preparation. If a patient lacks motivation to engage in these changes, their outcomes will be impaired. For patients who meet BMI criteria but lack readiness, motivational interviewing should be initiated before considering a surgical referral.

Adherence: Inability to adhere to pre- and postoperative guidelines (e.g., follow-ups, dietary guidance, vitamin supplementation) is a contraindication. Importantly, patients with cognitive impairment are not automatically excluded, provided they have a reliable and consistent support system in place.

Medical comorbidities: One of the notable aspects of MBS is the relative flexibility in accommodating patients with significant comorbidities. Individuals with conditions such as congestive heart failure or chronic kidney disease may still be excellent candidates, as obesity is often the underlying driver of these diseases. While compensated cirrhosis carries a slightly higher surgical risk, careful patient selection can mitigate complications. In many cases, the potential benefits of MBS, including improvements in the underlying disease, outweigh the risks. However, these risks must always be carefully weighed. Active malignancy, end-stage pulmonary disease, and other severely uncontrolled conditions generally pose too great a risk and should be addressed before proceeding with surgery.

Substance use: Active tobacco use is a contraindication due to the increased risk of poor healing and anastomotic ulcers. Most programs and insurers require complete cessation at least six weeks prior to surgery, often confirmed with urine nicotine testing. Marijuana use is surgeon-dependent but may be a barrier. Active alcohol or drug use is also a contraindication, though a past history of use is not. Postoperative risk of alcohol use disorder increases two to threefold, particularly with bypass procedures, likely due to a rapid and increased absorption and addiction transference. Psychological screening and support are essential to mitigate these risks. Patients with a history of food addiction are also at risk for transferring addictive behaviors to other vices, such as alcohol, gambling, or compulsive shopping.

Ultimately, determining a patient’s candidacy for MBS depends on the multidisciplinary team’s assessment of whether the potential benefits outweigh the risks. However, if any of the factors outlined above are present in a patient’s medical history, it is important to address them early and have an open discussion if MBS is being considered. Once eligibility is established, the next step involves a comprehensive preoperative evaluation, including physical, medical, and laboratory assessments, which will be covered in next week’s (part 2) blog.

Sample Question

A surgeon has collaborated with an anesthesiologist for preoperative evaluation for patients planning to undergo metabolic and bariatric surgery. The assessment will be completed one week before the surgery date. Which patients should have surgery delayed or canceled due to an elevated perioperative risk?

A. A patient over the age of 65 years old with sleep apnea

B. A patient who quit smoking cigarettes 3 months ago

C. A patient with factor 5 Leiden deficiency on apixaban

D. A woman who stopped oral contraceptives 1 week ago

Next Week: Part 2 (Preop Eval): Cardiac, Labs, and Preoperative Testing

Following Week:Pediatrics: Bullying, Stigma, and Food Insecurity

Upcoming: Knowledge Check

For more practice questions, check out the following:

  • Obesity Medicine Board Review Questions (2026): Qs 216, 248, 274, 283, 286, 288, and 325.
  • Obesity Medicine Practice Tests (2026): Qs 238, 312, 345, 381, and 425.

(Copyright 2026) Obesity Medicine Board Review Questions, LLC: obesitymedicinereview.com

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