Summary: A growing number of researchers are urging that the body mass index (BMI) be retired as a standard measure of health. This simple height-to-weight ratio is increasingly seen as outdated and misleading: it does not capture where fat is stored, how much muscle someone has, or important factors such as age and ethnicity. Despite these shortcomings, BMI continues to shape clinical decisions, insurance criteria, and public perceptions of bodies.
A new study led by researchers at the University of Waterloo recommends that policymakers and clinicians stop relying on BMI and instead adopt broader, more accurate indicators of health. The authors argue that redefining how we measure wellness is essential to reduce stigma and improve equitable care for diverse populations.
Key Facts:
- Outdated Metric: BMI originated as a simple statistical ratio and was never developed to be a comprehensive health assessment.
- Negative Impacts: Using BMI as a proxy for health can reinforce stereotypes, limit access to care, and contribute to stigma—particularly for people who are racialized, disabled, older, or live in larger bodies.
- Moving Forward: Researchers recommend replacing BMI with measures that reflect actual health outcomes, such as metabolic markers, body composition assessments, and lifestyle indicators.
Source: University of Waterloo
As recent Statistics Canada figures show that roughly two-thirds of Canadians fall into overweight or obese BMI categories, experts say this is the right moment to reassess how we define and measure health—starting with BMI.
For decades, BMI has been treated as a convenient shorthand across public health, clinical practice, and consumer technology. It is easy to calculate and widely understood, which is why it appears in everything from fitness trackers to decisions about surgical eligibility and pain management. But the Waterloo-led study makes a strong case that BMI paints only a partial and sometimes harmful picture of a person’s health.
“It’s increasingly clear that BMI doesn’t measure what many people assume,” said Dr. Aly Bailey, lead author and professor in the Department of Recreation and Leisure Studies at the University of Waterloo. “BMI cannot tell the difference between muscle and fat, misses where fat is located on the body, and overlooks age, sex and racial differences. Two people with the same BMI can have very different health profiles.”
The research team highlights the concrete consequences of depending on BMI: it can affect who receives certain medical treatments, entrench harmful ideas about which bodies are ‘normal,’ and deepen weight stigma. Those who already face discrimination—because of race, disability, age, or body size—are most likely to be harmed by policies that rely on this single metric.
BMI’s roots stretch back to the 19th century as a statistical tool for identifying an “average” body, not as a clinical measure of health. The study emphasizes that the metric’s history includes uses that reinforced racist and discriminatory ideas about bodies, and that history should be acknowledged when discussing its current use.
Responding to calls from activists and scholars, the paper describes several possible next steps. One option is to continue using BMI but with clear caveats and historical context. Another is to adopt more nuanced measures of body size and health—such as body composition scans, waist-to-height ratios, metabolic health indicators, and assessments of diet and physical activity. The authors most strongly recommend abandoning BMI altogether in favor of tools that better reflect overall health and reduce stigma.
Key Questions Answered:
A: Its simplicity and widespread adoption have made BMI an easy default. However, convenience does not make it scientifically robust for assessing individual health.
A: BMI does not distinguish between fat and muscle, ignores fat distribution, and was developed with assumptions about an “average” body that do not apply across genders, ages, and ethnic groups.
A: Researchers suggest using a mix of tools—body composition measurements, metabolic health markers, and lifestyle assessments—to form a more accurate and fair picture of a person’s health.
About this BMI, health, and neuroscience research news
Author: Ryon Jones
Source: University of Waterloo
Contact: Ryon Jones – University of Waterloo
Image: The image is credited to Neuroscience News
Original Research: Open access.
“The body mass index: What’s the use?” by Aly Bailey et al. Body Image
Abstract
The body mass index: What’s the use?
BMI is a pervasive metric in body image and health research—used as a correlate, covariate, or descriptive statistic. Yet the measure’s problematic history and limitations are often overlooked. Originally adapted from 19th-century statistical work, BMI became repurposed as a shorthand for health despite not being designed for that role.
Early users of these statistical ideas applied them to rank and exclude bodies, and over time BMI has been deployed in ways that reinforce white, masculine standards and discriminatory practices in insurance and healthcare. Body image scholars and health professionals must recognize this context if their goal is to challenge harmful beauty ideals rather than unintentionally validate them.
Within research, BMI has helped illuminate relationships between body size and both negative and positive body image. Still, its widespread and often uncritical use obscures the deeper issue: discrimination based on body size and persistent weight stigma.
Drawing on critical scholarship about the “use” of metrics, the authors explore when BMI helps, when it misleads, and when it should be set aside. They offer guidance on how to be a critical user—or an outright refuser—of BMI, and call for methods that center lived experience, equity, and meaningful health outcomes.