Is it time to trade in BMI for body roundness?

Medical standards and practices have come a long way from the 1800s, but apparently not when it comes to calculating patients’ weight risks.
 
Body mass index (BMI) was created in 1832 by a statistician and based on the ‘average man’, but is still widely used today to assess someone’s weight status – as either underweight, normal, overweight or obese.
 
This measurement has been called into question numerous times over the years, but no other estimate has emerged that is more prolifically used in healthcare settings for assessing patients’ weight.
 
But is it time for GPs to put aside the BMI?
 
Recently a new system of measurement has been attracting attention as a promising new anthropometric measure – the body roundness index (BRI).
 
The BRI works to establish the volume of visceral adipose tissue by determining someone’s ‘roundness’ by associating the body’s girth with height.
 
Earlier this year, a study of 33,000 United States adults and the association between BRI and all-cause mortality found both lowest and highest BRI groups experienced significantly increased risk of death.
 
But it is not as simple as trading in the BMI wholesale for the BRI, says Chair of RACGP Specific Interests Obesity Management, GP and dietitian Dr Terri-Lynne South.
 
Dr South told newsGP that although GPs have been historically overly reliant on BMI, the BRI presents its own limitations.
 
‘It’s hard enough to do a BMI but I think it can be even harder to do a waist measurement,’ she said.
 
‘The definition of where to measure appropriately a person’s waist does have differences in opinions.’
 
However, Dr South does not endorse BMI as a comprehensive approach either.
 
‘We know that BMI is correlated to metabolic health, but the actual causation is a lot more complicated,’ she said.
 
‘You can have two different bodies with a high BMI but, depending on their body composition, they’ll have very different metabolic health risks.’
 
Instead, she says GPs should use these kinds of measurements as part of a holistic approach.
 
‘We should still use the BMI, but move it to a screening tool, and then add on to that other measures, whether it is waist circumference, blood pressure, pathology or blood tests, so we’re not just using a single measure to label a person from an obesity point of view,’ she said.
 
Dr South argues for an overhaul of categorical systems, classing people into silos of underweight or overweight, and instead base interventions on risk.
 
‘We need to be starting to move away from labelling people in those categories,’ she said.
 
‘I think we’ve got a long way to go as we’ve been stuck in using healthy weight range and BMI for management purposes for so long.
 
‘It’s going to take some groundswell to shift that to be a more individual and holistic assessment, but I think we’ll get there.’
 
The process behind weight assessment, Dr South believes, could progress much like cardiovascular risk.
 
‘We used to talk about total cholesterol with patients 15-plus years ago, and be making decisions based on total cholesterol,’ she said.
 
‘Now we’re looking a lot broader, there’s a whole lot more parameters, and I expect that obesity management will eventually get to that point.’
 
But Dr South says there is a lot of work to be done before it gets there.
 
‘This space is significantly changing as is our understanding of obesity as a chronic complex condition,’ she said.
 
‘It has significantly changed just within my professional lifetime, and I think it’s going to take a lot of education and upskilling of all healthcare professionals, let alone the public.’
 
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BMI body mass index metabolic medicine obesity overweight overweight and obesity preventive health stigma