by Eesha Rehman

Graphic design by Qingyue Guo

You are obese. You have obesity. 

Are these two statements different? According to body mass index (BMI), they are not. 

In a 2022 Statistics Canada survey, approximately one-third (33%) of Canadian adults have obesity, as classified by a BMI greater than 30.¹ However, is BMI the ideal metric to assess whether an individual has obesity? Does being obese equate to having obesity? 

Two patients with BMIs over 30 can have markedly opposing health outcomes, despite both being in the ‘obese’ category. BMI does not account for differences in weight by fat or muscle. In accordance with the BMI criteria, an active plus-sized fashion model and a sedentary office worker are both obese, and in accordance with the Statistics Canada survey, they also have obesity. The BMI criteria define obese akin to obesity, yet the model could have an arguably lower health risk profile due to their active lifestyle than, let’s say, a lethargic, overworked graduate student with a “normal” BMI. 

Thus, the measure of weight requires a more nuanced definition to address the myriads of body types to correctly identify those at risk for obesity. BMI is a metric that assesses the size of the person rather than addressing their health concerns. A refined definition could promote acceptance in society of body variance, instead of an exclusive mold that generates black and white categorical associations of obesity via height and weight. 

Background of BMI 

The original purpose of BMI, developed by mathematician Adolphe Quetelet nearly 200 years ago, was to find l’homme moyen (the average man).² His goal was to determine the ideal height and weight of the Caucasian male. In the 1970s, American physiologist and dietician, Ancel Keys, advocated for what was then called the Quetelet Index to quickly screen for obesity, which quickly popularized to BMI.²

Currently, BMI values have been used by scientists, clinicians, and companies alike to categorize people’s risk of developing cardiovascular disease and diabetes. BMI is quick and easy to compute, yet its simplicity blinds the whole truth of health. BMI covers a mere iota of the multifaceted complexities of human health and disease. 

Why Change BMI? 

Currently, BMI is the basic measurement utilized in understanding global trends regarding weight and healthy living, making it easier for government and statisticians to interpret results. Height and weight are relatively easy measurements to procure, hence increasing its accessibility and reproducibility. Yet are these results reliable with real-world validity, or are they skewed to over-simplification? 

Consider real-world variation such as age, sex, and ethnicity that have differing, but meaningful, impacts on body composition and disease risk. For example, women tend to have a higher fat percentage in their hips and abdominal area, however, that fat has been found to provide health protective effects such as hormone regulation.³ People of Polynesian descent with high BMI tend to have less fat on their bodies than Europeans with the same BMI, attributing to differences in muscle mass.⁴ The obesity metric gap in clinical and research policies and procedures diminishes and ignores the health profiles of other groups. 

Current Consequences

In research, BMI is a common metric to collect when conducting population-based health estimates/studies. BMI can be compared with an array of other metrics such as incidents of cardiovascular disease, quality of life, and others. However, an alarming number of studies do not factor the influence of external variables such as diet and exercise in their analysis of BMI. What if poor diet and exercise cause both high BMI and increased mortality risk, rather than just BMI directly? Translational health research informs medical practice. Therefore, the negative implications of misinterpreted results in misguided health suggestions and practices serve no clinically significant benefit. 

Moreover, the effects of BMI are greater in the clinical field due to its commonality in various assessments. BMI is a universal measurement reported on medical reports, and healthcare practitioners in their hectic schedule may tend to make assumptions regarding the patient’s health based on their BMI categorization. For instance, if a patient comes in with complaints about heart issues, a physician may see a BMI greater than 30 and assume that they need to lose weight to resolve the issue, ignoring the fact that it may be some other underlying cause. The utilization of BMI as the rationale for medical issues severely limits the quality of care received, reducing the patient to one aspect of their health.  

Lastly, this number is used by health insurance companies to determine eligibility for medical-related expenses. They can increase their premiums for patients labelled with high risk of disease based on their BMI. 

Moving Forward with BMI 

BMI is a universal measurement. It has deeply rooted itself in the medical field and cannot be uprooted and replaced easily. Additionally, BMI in a general capacity does demonstrate an overall pattern, however for individual treatment BMI should be one part of the mosaic of health. Researchers and clinicians both need to expand their criteria for diagnoses of obesity and be less conservative in their diagnoses of diseases related to excess adipose tissues (i.e. fat cells). 

In 2023, the American Medical Association stated that BMI is “is “an imperfect way to measure body fat in multiple groups given that it does not account for differences across race/ethnic groups, sexes, genders, and age-span.”⁵

Hence, a more inclusive definition of obesity should not just include BMI as a criterion, but also look at percentage of excess adipose tissues, hormone fluctuation, and metabolic syndromes. A more holistic definition of the disease will encompass the multifaceted nature of obesity rather than as a BMI-defined disease. 

References 

American Medical Association (AMA). 2023 June 14. AMA adopts new policy clarifying role of BMI as a measure in medicine. Chicago (IL): AMA. https://www.ama-assn.org/press-center/ama-press-releases/ama-adopts-new-policy-clarifying-role-bmi-measure-medicine

Public Health Agency of Canada. Obesity statistics in Canada: report [Internet]. Ottawa (ON): Government of Canada; 2025 Jun 5 [cited 2026 Feb 15]. Available from: https://www.canada.ca/en/public-health/services/publications/healthy-living/obesity-statistics-canada.html.

Pray R & Riskin S. The History and Faults of the Body Mass Index and Where to Look Next: A Literature Review. Cureus. 2023;15(11). doi: 10.7759/cureus.48230.

Zhang C, Rexrode KM, van Dam RM, et al. Abdominal obesity and the risk of all-cause, cardiovascular, and cancer mortality: sixteen years of follow-up in US women. Circulation. 2008;117 doi: 10.1161/CIRCULATIONAHA.107.739714. 

Swinburn BA, Ley SJ, Carmichael HE, & Plank LD. Body size and composition in Polynesians. Int J Obes Relat Metab Disord. 1999;23(11):1178-83. doi: 10.1038/sj.ijo.0801053.