Body Roundness Index (BRI) vs. Body Mass Index (BMI)

Body Mass Index (BMI) has long been the standard metric for assessing body composition and obesity. However, the measurement is not perfect: it is unable to distinguish different types of body fats and does not account for crucial factors such as sex, muscle mass, and height. Alternatives to BMI have been a prominent research topic since the turn of the century. Scientists are interested in developing a more precise measurement that is able to more accurately predict the relationship between obesity, mortality, and diseases such as cardiovascular disease, hypertension, insulin resistance, and diabetes (1). Anesthesiology, a field which requires a detailed, individualized understanding of the body in order to ensure patient safety, is among several areas of medicine that would benefit from an alternative measurement to BMI, such as the Body Roundness Index (BRI).

BMI is calculated as weight (kg) divided by height squared (m²). Although it is an easy calculation that is widely used, BMI fails to account for body fat distribution or muscle mass. In anesthesiology, where fat distribution can influence airway management, drug pharmacokinetics, and ventilation strategies, this lack of precision can be problematic. For example, patients with central obesity (fat concentrated in the abdomen) may have a higher risk of difficult intubation, a risk not captured by BMI alone (2).

The Body Roundness Index (BRI) incorporates body shape and fat distribution into its assessment by using height and waist circumference to estimate the percentage of total body fat and visceral adiposity. Unlike BMI, BRI provides a more nuanced understanding of how fat is distributed, which is particularly relevant in the perioperative setting. Research suggests that BRI more accurately reflects visceral obesity, which puts patients at higher risk for disease (3). It also more accurately estimates risks for various clinical end points, including cardiometabolic disease, kidney disease, and cancer, all of which may impact anesthetic management (4).

Recent studies comparing BMI and BRI in clinical settings have highlighted BRI’s superiority in predicting obesity-related complications. In a study of hypertensive patients, BRI was found to be a better predictor of diabetes risk compared to BMI, having stronger associations with markers of abdominal obesity and insulin resistance (5). Animal studies suggest that some anesthetics result in insulin resistance, raising an important question for future research and a potential benefit to using BRI in anesthesia management (6). Studies continue to explore the usefulness of BRI not only as a metric to predict obesity but to highlight further complications that providers should be alert of, assisting in improving patient safety in both anesthesiology and other fields of medicine.

Despite its advantages, BRI is not yet as widely adopted as BMI, partly due to the need for additional measurements like waist circumference which complicate the calculation. However, as electronic medical records and imaging technologies improve, integrating BRI into routine clinical practice could become more feasible (7).

While BMI remains a useful screening tool, BRI offers a more comprehensive assessment of the body, which is particularly relevant for anesthesiology. By evaluating fat distribution and its implications, BRI could significantly enhance patient safety and outcomes in the perioperative setting.

References

  1. Pray, R., & Riskin, S. (2023). The history and faults of the body mass Index and where to look next: a literature review. Cureus. https://doi.org/10.7759/cureus.48230
  2. Seyni-Boureima, R., Zhang, Z., Antoine, M. M., & Antoine-Frank, C. D. (2022). A review on the anesthetic management of obese patients undergoing surgery. BMC Anesthesiology, 22(1). https://doi.org/10.1186/s12871-022-01579-8
  3. Kuk, J. L., Katzmarzyk, P. T., Nichaman, M. Z., Church, T. S., Blair, S. N., & Ross, R. (2006). Visceral fat is an independent predictor of all‐cause mortality in men. Obesity, 14(2), 336–341. https://doi.org/10.1038/oby.2006.43
  4. Zhang, X., Ma, N., Lin, Q., Chen, K., Zheng, F., Wu, J., Dong, X., & Niu, W. (2024). Body roundness Index and All-Cause Mortality among US Adults. JAMA Network Open, 7(6), e2415051. https://doi.org/10.1001/jamanetworkopen.2024.15051
  5. Liu, Y., Liu, X., Guan, H., Zhang, S., Zhu, Q., Fu, X., Chen, H., Tang, S., Feng, Y., & Kuang, J. (2021). Body roundness index is a superior obesity index in predicting diabetes risk among hypertensive patients: a prospective cohort study in China. Frontiers in Cardiovascular Medicine, 8. https://doi.org/10.3389/fcvm.2021.736073
  6. Yasuda, Y., Fukushima, Y., Kaneki, M., & Martyn, J. J. (2012). Anesthesia with propofol induces insulin resistance systemically in skeletal and cardiac muscles and liver of rats. Biochemical and Biophysical Research Communications, 431(1), 81–85. https://doi.org/10.1016/j.bbrc.2012.12.084
  7. Schweitzer, K. (2024). Could the body roundness index one day replace the BMI? JAMA. https://doi.org/10.1001/jama.2024.20115