Study Finds BMI May Do More Harm Than Good in Assessing Health

For decades, a person’s Body Mass Index, or BMI, has been treated as the gold standard in measuring their health. According to experts, it helps find out all about their physical standards, fitness, and associated

health issues. But maybe, no more. According to a new Waterloo-led study, BMI only tells a fraction of the story about a person’s health and does more harm than good when used. “It is becoming more well-known that BMI doesn’t measure what many people think it does,” said Dr Aly Bailey, the lead author of the study and a professor in the Department of Recreation and Leisure Studies at Waterloo. Dr Bailey said BMI cannot distinguish between muscle and fat and is not able to account for where fat is distributed in the body, while overlooking many important factors like age, sex, and race. “Two people can share the same BMI but have completely different health profiles,” she said.

BMI limitations have real-world consequences

According to the scientists, these limitations of BMI can have consequences, as it influences access to medical care and reinforces harmful stereotypes about what “normal” bodies are. It also contributes immensely to stigma, where mostly people are racialized, disabled, older, and have bigger and larger bodies. “What many people often don’t know is that the BMI was never created with health in mind at all,” Bailey said. “Instead, it was a statistical tool used to justify racist and anti-fat ideas and other forms of discrimination. It quickly became a so-called measure of health, beauty, and fitness.” It is believed that BMI was originally developed in the 19th century to statistically identify the “average man,” making it a measure based on height and weight.

What is the way forward?

The study, recently published in the journal Body Index, suggests that there are many possible paths forward to counter BMI as the only way to measure your health and fitness. One approach is to continue using BMI - but only with explicit recognition of its racist and problematic history. However, another is to consider more nuanced and valid measures of body size or include indicators that track actual health outcomes. The other, bolder option, which the authors advocate the most strongly, is to reject BMI altogether. Many experts have also suggested using BMI in conjunction with other measures of risk, like visceral fat - found deep within the abdominal cavity, the body adiposity index - based on hip and height measurement, body composition - the percentage of fat, bone, and muscles, and genetic and metabolic factors, among others. Scientists believe that the person with more belly fat would have a greater waist circumference, associated with a higher risk of heart disease, diabetes, and liver problems.