Body fat over BMI for obesity diagnosis: Study

Using body mass index (BMI) alone as a method for obesity diagnosis could be leaving vulnerable patients going without the care they need, according to new international research.
 
Instead, the study, published in Nature Medicine, is calling on medical professionals to focus on body fat distribution to paint a more accurate picture of a patient’s overall health.
 
In terms of condition management, they add that obesity interventions should be considered for those with a waist-to-height ratio higher than 0.5, which would help people in need who fall below the obesity BMI cut-off level of 30.
 
‘In many settings, the diagnosis of obesity is still based solely on BMI cut-off values and does not reflect the role of adipose tissue distribution and function in the severity of the disease,’ the study concluded.
 
On Monday, the researchers launched their new framework for the diagnosis, staging, and management of obesity in adults, which includes the ‘new generation of obesity medications’.
 
This framework labels the use of BMI alone in obesity diagnosis as ‘insufficient as a diagnostic criterion’, saying that body fat distribution has a much more substantial effect on health.
 
Once a patient has been diagnosed under this new framework, researchers then suggest GPs discuss personalised therapeutic targets with the patient, implement an initial level of intervention, and then an intensification of therapy if needed.
 
Dr Natasha Yates, a Queensland GP and Medical Education Assistant Professor at Bond University, welcomed the research, saying many doctors have long been calling for BMI to be abandoned.
 
‘It’s a very imperfect tool, and the problem is that a lot of research has been done using BMI, so when we’re trying to practice according to guidelines, we’re backed into a corner,’ she told newsGP.
 
‘But we’ve known for a long time that waist measurement is more accurate at predicting cardiovascular risk, and so a lot of GPs are already using that.
 
‘This will help make sure we’re not missing those patients who are in the BMI range between 25 and 30 who we’ve really wanted to treat but we’ve struggled to have good options for them.’
 
BMI continues to be the most common measure of obesity across the globe, with the World Health Organization defining a person with a BMI of more than 25 to be overweight, and more than 30 as obese.
 
Using this metric, Australia is currently ranked 10th out of 21 OECD countries for the proportion of people aged 15 and over living with overweight or obesity, with the conditions impacting around 26% of children and 66% of adults.
 
For doctors, the framework recommends nutritional therapy, physical activity, stress reduction, and sleep improvement as the ‘main cornerstones of obesity management’, as well as potential for psychological therapy, obesity medications, and metabolic or bariatric procedures.
 
It also proposed the use of obesity medications in patients with a BMI of 25 kg/m2 or higher and a waist-to-height ratio of above 0.5, who also have medical, functional, or psychological impairments or complications.
 
But Dr Yates said the broadness of these definitions could become challenging for GPs in making a diagnosis.
 
‘Medical, I think, is quite easy to pin down, but functional and psychological can be more nebulous, so that might be where there’s a bit of a challenge for us,’ she said.
 
‘But as a whole, GPs will find this quite refreshing because it’s more aligned with what we’re actually doing.’
 
The framework says this change in treatment must serve as a call to pharmacological companies and regulatory authorities to be less reliant on traditional BMI cut-offs.
 
‘This statement will move obesity management closer to the management of other non-communicable chronic diseases, in which the goal is not represented by short-term intermediate outcomes, but by long-term health benefits,’ researchers concluded.
 
‘Defining long-term personalised therapeutic goals should inform the discussion with the patients from the beginning of the treatment.’
 
Dr Yates said bringing up weight with patients remains a sensitive topic for GPs to navigate, but her advice is to remember each individual patient is a ‘human being who is complicated’.
 
‘There is no strict rule, but if their weight is directly affecting the reason they have come to you, then at some point you should try to bring it up, but you also need to read the patient well and work out if this is going to be helpful,’ she said.
 
‘The core of general practice is building long-term relationships and trust, and if you break someone’s trust by bringing it up because you think it’s important, you’ve actually undermined your ability to help them.
 
‘You may have been correct technically, but you’ve actually not helped the person in the long-term.’
 
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