Beyond BMI: Alternative Measures of Body Size or Composition to Utilize in Behavioral Medicine

Jennifer K Frediani PhD, RD, ACSM-CES¹; Katherine Balantekin PhD, RD²; Faith A Heeren BA³; Leah M Schumacher, PhD⁴; Jacqueline Hayes⁵ - Obesity and Eating Disorders (OED) SIG

Many behavioral medicine researchers, clinicians, and policymakers are interested in better understanding whether an individual’s weight status and/or body composition places them at increased risk for negative health outcomes.

Body mass index (BMI) is frequently used to assess and quantify weight-related health; however, its limitations have resulted in calls for better alternative measures. Below, we provide a brief history, strengths and limitations, and potential alternative measures for assessing weight- or body fat-related aspects of health.

Historical Context and Modern Adaptation of BMI

The Quetelet index was originally derived to quantify the “normal man” in 1832 by statistician Adolphe Quetelet. In 1972, after conducting a study that primarily sampled white men, Ancel Keys renamed the measure to body mass index (BMI) and recommended it as a tool for assessing relative weight.¹ A driving factor in its adoption was its use by life insurance companies to establish 'standard' or 'ideal' weight. In the late 1990’s, the World Health Organization and the National Heart, Lung and Blood Institute proposed utilizing the BMI cut-points routinely used today to diagnose underweight and overweight/obesity.²  

Strengths and Limitations of BMI

BMI is cheap, easy to use, and requires no specialized equipment. As such, it is easy to implement in clinical practice, research studies, and even self-assessment of weight-related health with online calculators. At a population level, it is associated with a number of health conditions.³

BMI has several significant limitations that largely stem from its applications in individuals. One major issue is its inability to distinguish between fat distribution and muscle mass. Another is potential inaccuracies in its use across individuals of different identities given its origins in primarily white men.¹ Finally, BMI cut-offs are somewhat arbitrary and do not account for other relevant factors that influence health at a patient-level.²

Alternative Measures to BMI

Given the limitations of BMI, alternative measures of weight- or body fat-related health are warranted. The American Medical Association recommends measurements such as visceral fat, body adiposity index, body composition, relative fat mass, waist circumference (WC), and genetic/metabolic factors.⁴ Of note, some of these measures can be cumbersome, especially in clinical settings or fieldwork, and may have more pragmatic applications in research and/or specialty clinical settings.

One promising easy-to-use measure is the waist-to-height ratio, which has shown good correlation with cardiometabolic risk and may be a better option than WC, as it accounts for height.⁵ However, more data is needed to establish useful cutoffs. Two other indices, the Body Roundness Index (BRI) and the Body Shape Index (ABSI), are gaining traction and proving easy to use in clinical settings. Reference ranges are still being determined for different conditions.⁶ The ABSI is calculated by dividing waist circumference by BMI and height and there is not yet a cut off established. BRI is more complicated and uses constants, waist circumference and height. Both measures have been validated in diverse samples and are predictive of metabolic syndrome and hypertension, with BRI performing better than ABSI.⁷

Another index associated with cardiometabolic diseases such as type 2 diabetes, metabolic syndrome, and chronic kidney disease is the Lipid Accumulation Product (LAP) index. LAP is calculated using waist circumference and triglyceride blood levels with different constants for biological men and women. LAP serves as a moderate predictor for chronic kidney disease⁸ and is strongly associated with type 2 diabetes, outperforming BMI but comparable to waist-to-hip and waist-to-height ratios.⁹ In individuals with metabolic syndrome, LAP has shown stronger predictive capabilities than BMI, waist-to-height or waist-to-hip ratios, BRI, ABSI, body adiposity index, and conicity index across both sexes.¹⁰

Conclusion

While BMI remains a widely used tool due to convenience, low cost, and ability to correlate potential health risks at a population level, its limitations warrant the consideration and incorporation of alternative measures into research and clinical practice. Indices like waist-to-height ratio, BRI, ABSI, and LAP can provide more nuanced insights into an individual's health risks and should be considered as part of research and clinical evaluations as feasible.

Affiliations:

1. Nell Hodgson Woodruff School of Nursing, Emory University
2. Department of Exercise and Nutrition Sciences, University at Buffalo
3. Department of Health Outcomes and Biomedical Informatics, University of Florida
4. Department of Social and Behavioral Sciences, College of Public Health, Temple University
5. Department of Psychiatry and Human Behavior, Brown University; Weight Control and Diabetes Research Center, The Miriam Hospital

References:

1. Blackburn H and Jacobs Jr D. Commentary: Origins and evolution of body mass index (BMI): continuing saga. Int J Epi. 2014; 43(3):665-669.
2. Flegal KM. Use and misuse of BMI categories. AMA J Ethics. 2023; 25(7):e550-558.
3. Centers for Disease Control and Prevention. “About Body Mass Index (BMI).” May 20, 2024. https://www.cdc.gov/bmi/about/index.html#:~:text=BMI%20for%20population%20health,and%20track%20changes%20over%20time.Accessed October 22, 2024.
4. AMA press release. AMA adopts new policy clarifying role of BMI as a measure in medicine. June 14, 2023. https://www.ama-assn.org/press-center/press-releases/ama-adopts-new-policy-clarifying-role-bmi-measure-medicine Accessed September 24, 2024.
5. Chan V, Cao L, Wong MMH, Lo K, Tam W. Diagnostic accuracy of waist to height ratio, waist circumference, and body mass index in identifying metabolic syndrome and its components in older adults: a systematic review and meta-analysis. Curr Dev Nutr. 2023; 8(1): 102061.
6. Zhang X, Ma N, Lin Q, Chen K, Aheng F, Wu J, Dong X, Niu W. Body roundness index and all-cause mortality among US adults. JAMA Netw Open. 2024; 7(6):e2415051.
7. Calderón-García JF, Roncero- Martín R, Rico- Martín S, De Nicolás-Jiménez J, López-Espuela F, Santano-Mogena E, Alfageme-García P, SánchezMuñoz-Torrero JF. Effectiveness of body roundness index (BRI) and a body shape index (ABSI) in predicting hypertension: a systematic review and meta-analysis of observational studies. Int J Environ Res Public Health. 2021; 18(21): 11607.
8. Wu F, Cui C, Wu J, Wang Y. Association between lipid accumulation product index and chronic kidney disease: a systematic review and meta-analysis. Exp Ther Med. 2024; 28(2): 308.
9. Ayundini G, Astrella C, Tahapary D, Soewondo P. A systematic review on the association between lipid accumulation product index and type 2 diabetes mellitus. J ASEAN Fe Endocr Soc. 2019; 34(1): 16-20.
10. Witarto BS, Witarto AP, Visuddho V, Wungu CDK, Maimunah U, Rejeki PS, Oceandy D. Gender-specific accuracy of lipid accumulation product index for the screening of metabolic syndrome in general adults: a meta-analysis and comparative analysis with other adiposity indicators. Lipids Health Dis. 2024; 23(198):947.