Introduction

For decades, Body Mass Index (BMI) has been the go-to measure for assessing an individual’s health based on their weight. Whether at routine doctor’s appointments or through countless online calculators, BMI has become a quick health check for millions. In fact, companies like Zerodha have even incentivized employees with a BMI under 25. But recent studies suggest that BMI may no longer be the best indicator of health, giving rise to a new metric: Body Roundness Index (BRI).

This shift from BMI to BRI is driven by increasing awareness that BMI oversimplifies health assessments, ignoring critical factors like fat distribution and muscle mass. Let’s explore why BMI may be losing relevance and why BRI might be a better predictor of health risks.

The Limitations of BMI

• BMI, which is calculated by dividing one’s weight in kilograms by the square of their height in meters, has been used for years to categorize individuals into weight classes: underweight, normal, overweight, and obese.
• A BMI between 18.5 and 24.9 is considered “normal,” while a BMI over 30 is classified as obese. However, experts have raised several issues with BMI as a measure of health.
• One of the major limitations of BMI is that it does not account for body composition. It tells us nothing about the proportion of muscle, fat, or water in the body. This can lead to misleading conclusions.
• For instance, athletes with high muscle mass might have a high BMI, but they are often very healthy.
• Additionally, BMI fails to consider where fat is stored in the body, which can be crucial in predicting health risks. “It cannot be assumed that a high BMI always means high fat,” notes Jaichitra Suresh, Chief Medical Officer at SIMS Hospital in Chennai.

Moreover, BMI was developed based on data from 19th-century Europeans, making it less accurate for people from different ethnic backgrounds. For example, an Indian and a Caucasian with the same BMI may have vastly different fat compositions, with the Indian likely having a higher fat percentage. This is why many experts are now advocating for alternative measures like the BRI.

Enter Body Roundness Index (BRI)

• BRI, introduced by U.S. mathematician Diana Thomas in 2013, offers a more nuanced understanding of health by factoring in waist circumference and body fat levels, in addition to height.
• It addresses one of the main criticisms of BMI: it doesn’t just measure weight but looks at how round the body is. The more round a person is, the more visceral fat they are likely to have, which is a key predictor of health risks such as diabetes and cardiovascular problems.
• Unlike BMI, which uses a simple formula, BRI calculates the percentage of body fat and provides a visual representation of the body’s shape.
• A score between 1 and 15 is assigned, with scores over 6.9 or under 3.41 considered to be at higher risk for illnesses. “The more round you are, the higher your body fat percentage and risk of diseases,” says Dr. Thomas.

The Importance of Fat Distribution

• Where fat is located in the body is as important, if not more, than how much fat a person has. Studies have shown that fat stored in the abdominal area, particularly around the internal organs (visceral fat), is a major risk factor for metabolic diseases such as type 2 diabetes and cardiovascular problems.
• BMI does not capture this risk, which is why it can be misleading. As Dr. Anura Kurpad, professor of physiology at St. John’s Medical College, explains, “You could be skinny but have a paunch, which would put you at risk of non-communicable diseases.”
• Indians, in particular, are genetically predisposed to store fat around the abdomen, making them more susceptible to diabetes.
• This has led health organizations to suggest lowering BMI thresholds for Asian populations. For instance, the National Institute of Nutrition now considers a BMI of 23 to 27.5 as overweight for Asians, given their higher fat percentages.

BRI: A More Reliable Predictor?

• Several studies are now showing that BRI may outperform BMI in predicting health risks.
• For example, a 2021 study published in Diabetology International found that BRI had a significantly higher capacity to predict metabolic syndrome than BMI.
• Another study in JAMA Network Open of over 32,000 U.S. adults revealed that both the lowest and highest BRI scores were linked to increased mortality risk, suggesting that BRI may be a more accurate measure of overall health than BMI.
• That said, BRI is not without its challenges. It relies heavily on waist circumference measurements, which can be subject to human error.
• As Alice Bullas, Senior Research Fellow at Sheffield Hallam University, noted, even trained professionals often struggle to take accurate waist measurements. This margin of error could be even higher when people attempt to measure themselves at home.

Moving Beyond BMI

• While BMI has been a useful tool for decades, it is clear that it has significant limitations in accurately predicting health risks.
• BRI offers a more comprehensive view by taking into account fat distribution and body shape.
• However, both measures have their flaws and may need to be used in conjunction with other health assessments, such as waist-to-height ratios and body fat percentages.
• For now, experts like Dr. Kurpad recommend using simple tools, like the waist-to-height ratio, as a good rule of thumb.
• If your waist circumference is less than half your height, you’re likely in good shape. If it’s more, it may be time to take a closer look at your health.

Conclusion

As research continues to evolve, one thing is clear: when it comes to assessing health, there is no one-size-fits-all metric. Both BMI and BRI can provide valuable insights, but neither should be used in isolation. Taking a holistic approach that includes various measurements and lifestyle factors is key to understanding and maintaining good health.