How BMI is becoming an inadequate measure for health Premium

The debate between BMI and BRI as health indicators continues, with BRI showing promise in predicting health risks.

Practically everyone who has gone to a doctor for a check-up has had their BMI or Body Mass Index measured. BMI calculators abound online and it has become a modern go-to quick check for one’s health — financial services company Zerodha even announced, in 2022, an extra bonus for employees with a BMI of less than 25.

But how accurate is BMI in deciding how healthy you are now, or how healthy you will remain in the future? Increasingly, experts have arrived at the realisation that it is an imperfect calculation that has several limitations.

Therefore, the new buzz word is BRI or the Body Roundness Index. Devised by U.S. mathematician Diana Thomas, and first published in a 2013 paper, this index measures how round you are. “BMI is grounded by the assumption that bodies are like cylinders. But when I looked at myself in the mirror, I thought — ‘I’m more of an egg than a cylinder.’ And this is what led to devising the BRI” she says.

The mathematical formula for BRI is associated with body fat levels, and takes into account height and waist circumference. The scores usually range from 1 to 15, with those having very high scores or very low scores (of over 6.9 or under 3.41) considered at the most risk for illnesses.

BMI is your weight in kilograms divided by your height in metres squared. A BMI of 18 to 24.9 is considered normal; 25 to 29.9 is termed overweight and 30 and above is classified as obese.

The problem, says Jaichitra Suresh, chief medical officer, SIMS Hospital, Chennai, is that BMI does not help a doctor understand the composition of the weight: how much of it is fat, muscles or water for instance, and where the fat is distributed in the body. “Athletic people and those who do weight training may have high BMIs, as muscles are denser than fat, but will still be healthy. It cannot be assumed that a high BMI always means high fat,” she points out.

BMI also has limitations with different ethnic groups — it was created using data from 19th century Europeans. For instance, Dr. Jaichitra says, an Indian and a Caucasian may have the exact same BMI, but in an Indian the fat percentage may be higher than that of the Caucasian.