BMI: A Poor Metric for Top Surgery

When it comes to gender-affirming surgery, body mass index (BMI) is a poor metric for determining who should be approved for chest masculinization surgery (CMS) — also known as top surgery — according to a new study by researchers at the Johns Hopkins Center for Transgender and Gender Expansive Health (CTH).

“Despite the lack of solid evidence showing an association between a high BMI and serious postoperative complications in chest masculinization — such as blood clots, bleeding and infection — many people who are transgender and nonbinary get denied the surgery,” says Bashar Hassan, a postdoctoral research fellow in plastic and reconstructive surgery at the CTH and the University of Maryland Medical Center’s R Adams Cowley Shock Trauma Center.

To determine if the BMI barrier was appropriate, the CTH team reviewed demographics, operative procedures and postoperative complications for 2,317 people who are transgender or nonbinary, and who underwent chest masculinization surgery (as a primary surgery and not concurrently with another procedure) between 2012 and 2020.

Hassan explains that the previous studies used to set chest masculinization surgery eligibility criteria rarely included people with very high BMIs. “In contrast, our study evaluated one of the largest groups of CMS patients who belong to the morbidly obese and super-obese categories,” he says.

“We found that people with high BMIs did have a slightly increased risk of complications across the board, but that the risk for serious complications — those that were life-threatening — was very low,” says study senior author Fan Liang, CTH medical director. She adds, “Given that our large-scale study strongly suggests such a low risk for severe complications following CMS in people with high BMIs, we recommend that the medical community reevaluate its current approach of BMI cutoffs for CMS eligibility.”