Body Mass Index Requirements for Gender-Affirming Surgeries Are Not Empirically Based

Abstract

Body mass index (BMI) requirements for gender affirmation surgery (GAS) are ubiquitous and vary across providers. Requirement variation is not surprising given little data to suggest an association between BMI and GAS outcomes. Implementation of subjective BMI requirements limits access to GAS and negatively impacts patient health and safety. We outline the literature on BMI and GAS outcomes, discuss clinical utility of GAS, and summarize dangers of prescribing weight loss as a prerequisite for surgery. We propose that providers use empirically supported indices of health and comorbidity instead of BMI to determine surgical eligibility for all patients considering GAS.

Although the World Professional Association for Transgender Health (WPATH) guidelines for gender affirmation surgery (GAS) do not specify a body mass index (BMI) requirement,¹ providers performing these procedures often do. Many programs tell patients to lose weight before surgery and require the patient's BMI to be <30, 33, or 35 kg/m², or they evaluate individuals >30 kg/m² BMI on a case-by-case basis (e.g., Beth Israel Deaconess Medical Center²). Notably, medical insurance coverage is contingent on “medical conditions” being “reasonably well controlled” (e.g., Blue Cross Blue Shield of California³). Given the broader medical culture that often equates larger body size with poor health, such vague guidelines leave room for providers and programs to approximate how “controlled” medical conditions are by screening BMIs. Such criteria serve as barriers to essential surgeries⁴ and do not have an empirical basis.

BMI has been widely criticized as a marker of health or wellness due to its two-dimensional nature (i.e., weight/height²). Although a full critique is outside the scope of this article, it is worth mentioning that BMI persists into the modern day as a relic from a mathematician's efforts to categorize body weight in Europe during the 1800s. In particular, BMI as a determinant of health for nonwhite noncisgender bodies is profoundly problematic, as it was never validated in these populations. This is evidenced by a growing body of work questioning the validity of BMI within racial/ethnic minority communities.^5,6 Black individuals have been shown to have higher BMI on average than their white counterparts, and this disparity is not reflective of increases in visceral fat.⁷ Likewise, transgender and gender nonconforming (TGNC) folks tend to exhibit higher BMI⁴ for a range of reasons, including engagement in gender-affirming hormone treatment (notably, a year of which is a WPATH criteria for surgery),^1,8 decreased access to health-promoting resources (e.g., nutritionally dense foods, affirming spaces, and social environments supportive of physical exercise),⁹ and higher risk of binge eating and related disorders.¹⁰ As such, BMI requirements for GAS disparately impact TGNC and racial/ethnic minority communities compared with cisgender white communities.

It is well understood across disciplines that for those who wish to pursue medical transition, GAS profoundly improves health and safety outcomes. Such procedures have been shown to improve quality of life¹¹ by decreasing gender dysphoria, which is linked to negative mental health outcomes, including depression, disordered eating, suicidal self-directed violence, and trauma-related symptoms.^10,12 Furthermore, research shows that denying TGNC individuals timely access to GAS significantly increases their risk of suicidal ideation and attempted suicide,¹³ while also denying them access to the benefits of GAS, which include greatly reduced psychological symptoms and gender dysphoria.^11,14 GAS can also help individuals “pass” as the gender with which they identify, which in turn decreases the risk of bias-related victimization and discrimination.¹⁵ GAS procedures are clearly essential to the well-being and survival of TGNC individuals, and barriers to such treatment must not be taken lightly.

BMI Is Not a Predictor of GAS Outcomes

We recognize the variability of surgical procedures utilized in gender transition and that procedure choice is largely directed by patient preference. As such, there are gender-affirming procedures not specifically encompassed by this review. The literature cited to support BMI requirements for GAS includes a range of studies showing that BMI >30 kg/m² is associated with increased operative time due to technical difficulty, increased risk of surgical site infections, increased risk of postoperative arrhythmia, and other postoperative complications in surgeries that are mostly large abdominal, cardiac, and oncological.^4,16,17 That said, not all evidence suggests greater risk for higher weight individuals, as one orthopedic study found that underweight status (BMI <18.5 kg/m²) poses higher surgical risk of any adverse event, severe adverse event, or postoperative infection compared with normal-weight and overweight (BMI >24.9 kg/m²) categorizations, which had no relative increased risk.¹⁸ Most pertinent to this article, literature suggests that the most commonly pursued GAS procedures (genital and chest) can be safely performed on obese^* patients, defined by BMI >30 kg/m².

Penile inversion vaginoplasty is considered the gold standard for gender-affirming vaginoplasty, and a growing body of evidence suggests no difference in perioperative outcomes for patients with BMI >30 kg/m² as compared with those with BMI <30 kg/m².^19,20 Several retrospective reviews of patients who underwent penile inversion vaginoplasty found that BMI was not predictive of complications or need for revisions.^21,22 Although some studies, reflective of single-surgeon experiences, suggest BMI is associated with increased risk of complications, the odds ratio was notably lower than for other identified significant risk predictors.²³ Similar findings have been reported for masculinizing genital procedures. Although the selection of phalloplasty technique is influenced by BMI, complication rates for the approach preferred for patients with BMI >30 kg/m² are lower than for other accepted techniques.²⁴ In addition, BMI was not found to be predictive of complication risk for gender-affirming hysterectomy; American Society of Anesthesiologists (ASA) classification, a more comprehensive metric of health status, was found to better correlate with surgical outcomes.²⁵

Regarding gender-affirming mastectomy, existing evidence that BMI is a predictor of complications is mixed at best. Some data, reflective of single-surgeon experiences, indicate that higher BMI correlates with surgical risk; however, this association was found to be modest in comparison with other identified risk factors.²⁶ In contrast to this modest association, a large retrospective review demonstrated that patients with greater BMI do not have significantly higher odds of complications or revisions, which was consistently shown across all classes of “obesity.”²⁷ Also of note, BMI was not found to be predictive for all-cause complications of augmentation mammoplasty.²⁸

Risks of Weight Loss Prescription

Although providers often prescribe weight loss for patients with an elevated BMI seeking GAS, there is minimal empirical evidence that dieting and weight loss programs are effective for achieving significant and sustained weight-related outcomes,^29,30 and this has been specifically found in a sample of TGNC individuals denied GAS who were not able to gain eligibility through behavioral weight loss programming.⁴ Rather, patients who engage in dieting have been shown to gain significantly more weight than nondieters in the long and short term, contributing to a dangerous pattern of body weight destabilization known as weight cycling. Weight cycling is strongly associated with multiple negative health outcomes, including all-cause mortality, cardiovascular disease, immunosuppression, reduced bone mineral density, and chronic inflammation.²⁹

Furthermore, such messages from providers foster and perpetuate weight stigma. This contributes to a positive feedback loop of weight cycling through behavioral, physiological, and emotional stress responses³¹ and is also associated with increased frequency and severity of disordered eating behaviors (e.g., fasting, vomiting, and binge eating).³² These behaviors independently increase an individual's age-adjusted mortality rate, while associated nutritional deficiencies impede wound healing and increase risk of surgical site infections.^33,34 In addition, it is worth noting that GAS procedures could help patients decrease binge eating and other disordered eating behaviors associated with weight gain/cycling by decreasing gender dysphoria, which has been shown to be related to disordered eating behaviors.^10,12 Thus, providing as many people as possible access to GAS could help reduce weight cycling among TGNC individuals.

As TGNC individuals are at higher risk for self-reported disordered eating, depression, anxiety, and other mental health conditions,^10,12 prescribing weight loss may precipitate or exacerbate these conditions, potentially preventing such individuals from meeting WPATH mental health requirements for surgery.

Conclusion

We suggest that GAS providers question the prevailing assumption that BMI is a useful heuristic for approximating surgical risk, as a growing body of evidence indicates it has little utility in this context. Instead, we propose that providers use risk factors and health indices that are more predictive of GAS outcomes (e.g., ASA classification, breast volume, and presence of comorbidities). More broadly, requirements for GAS should not be arbitrarily set at the provider's discretion without considering the empirical basis. Without this critical step, providers run the risk of allowing weight-related bias to drive medical decisions. Furthermore, it is harmful to prescribe weight loss to meet BMI requirements, as TGNC individuals are at risk of many sequelae from such an intervention.^{10,12,29,32–34}

In the event that comorbidities correlated with higher BMI are present and confer significant surgical risk, we recommend a more guided approach to helping patients move toward GAS. For example, if cardiovascular risk is present, providers may suggest that TGNC patients seek support from TGNC-affirming dietitians and trainers to help them improve cardiovascular health through a multimodal human-centered approach.

It is also worth noting that a significant self-perpetuating gap exists in the literature evaluating outcomes for several GAS procedures. In studies not specifically designed to evaluate BMI as a risk factor for complications, TGNC patients with higher BMI are excluded, as they are deemed surgically unfit by institutional or surgeon-specific protocols.³⁵ In addition, arbitrary BMI requirements for surgery may disproportionately affect patients seeking GAS even when analogous procedures are performed in cisgender patients for cosmesis.²⁶ As the benefits of GAS are substantial and well described, further research is needed to identify more specific predictors of surgical risk in this understudied population to improve safety outcomes and maximize access to essential procedures for the TGNC community. Research and clinical practice are hindered by continued reliance on BMI as a requirement for GAS candidacy.

Abbreviations Used

ASA

American Society of Anesthesiologists

BMI

body mass index

GAS

gender affirmation surgery

TGNC

transgender and gender nonconforming

WPATH

World Professional Association for Transgender Health

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received to support this project.

Cite this article as: Brownstone LM, DeRieux J, Kelly DA, Sumlin LJ, Gaudiani JL (2021) Body mass index requirements for gender-affirming surgeries are not empirically based, Transgender Health 6:3, 121–124, DOI: 10.1089/trgh.2020.0068.