In daily practice, physicians need a quick and simple way to assess whether a patient’s weight presents a health risk. For decades, the body mass index (BMI) has been used for this purpose, with calculations based on height and weight. Despite its convenience, BMI has faced increasing criticism.
According to experts, BRI may more accurately identify people with high levels of visceral fat than BMI. It’s well documented that abdominal fat is strongly linked to higher risks for obesity-related diseases.
Studies Support BRI
Several studies have suggested that BRI could be a valuable tool for assessing health risks. In June of this year, researchers from China reported a significant U-shaped association between BRI and overall mortality in a paper published in JAMA Network Open. People with very low or very high BRI had an increased risk for death, noted Xiaoqian Zhang, MD, from Beijing University of Chinese Medicine, Beijing, China, and his colleagues.
A study published in September in the Journal of the American Heart Association showed that elevated BRI over several years was associated with an increased risk for cardiovascular diseases. “The BRI can be included as a predictive factor for cardiovascular disease incidence,” stated the authors, led by Man Yang, MD, from Nanjing Medical University in Nanjing, China.
Why Replace BMI?
Why is a replacement for BMI necessary? When asked by this news organization, Manfred Müller, MD, senior professor at the Institute of Human Nutrition and Food Science at the University of Kiel, in Germany, explained: “BMI was designed to provide a simple value that was as independent of body size as possible, that could detect obesity and estimate related disease risks. But scientifically, BMI has always been a very crude measure to characterize disease risks.”
Müller was part of a research group led by US mathematician Diana Thomas, PhD, who, at the time, worked at Montclair State University, Montclair, New Jersey, and now holds a position at the US Military Academy at West Point, in New York. The group developed and published the BRI in 2013.
BMI Classifies Bodybuilders as Obese
The researchers justified their search for a “better” anthropometric measure with two aspects of BMI that still constitute the main points of criticism of the widely used index today:
BMI incorrectly classifies individuals with significant muscle mass, like bodybuilders, as obese, as it doesn’t distinguish between fat and muscle mass.
BMI provides no information about fat distribution in the body — whether it’s concentrated in the hips or the abdomen, for example.
In practice, this means that a person with a normal BMI could already have prediabetes, high blood pressure, and high cholesterol, which might go undetected if no further investigations are conducted based solely on their BMI.
The BRI aims to solve this problem. As the name suggests, this index seeks to capture a person’s “roundness.” The formula for calculating BRI includes waist circumference and height but excludes body weight:
BRI = 364.2 − 365.5 × √(1 − [Waist circumference in cm/2π]²/[0.5 × Height in cm]²)
In their 2013 article, Thomas, Müller, and colleagues wrote that it still needed to be proven whether their newly developed index correlated with mortality and the risk for cardiovascular and metabolic diseases — and whether it was sufficiently better than BMI to justify the more complex calculation.