Many experts do not support the move, saying it was too soon to remove a key feature of anorexia, which has the highest mortality rate of any psychiatric condition.
«At first it sounds preposterous,» Professor Hay said. “Starvation and being severely underweight are hugely important in anorexia and we shouldn’t ignore that.
“But it has deeply affected how eating disorders are seen in the broader community and it has become an impediment for people who aren’t underweight seeking treatment and when they do, they are told ‘no, you are not thin enough’.»
One in five obese or overweight people have an eating disorder, previous research suggests.
It takes on average of 10 years for a person with an eating disorder to access appropriate support and an estimated 70 per cent currently do not receive evidence-based treatment.
The stereotype “young, thin, wealthy female” was an outdated 19th-century concept, Professor Hay said.
‘Atypical anorexia nervosa’ – characterised by severe weight loss and diet restriction in people with normal or above normal weight – was increasingly common given the average BMI of Australians was now in the overweight category, she said.
She argued “extreme weight loss” from any starting point, would be a more appropriate criterion.
One in 20 people with anorexia dies of their condition, which largely explains the clinical focus on severely underweight patients and their medical complications.
But eating disorder patients at higher BMIs were also at risk of dying from medical complications associated with extreme weight loss, purging, overeating, as well as suicide.
“Why not start again and classify eating disorders on the basis of common biological, genetic and psychological and other defining features,” Dr Hay said.
She said the shift would help close the large treatment gap and move beyond the cultural focus on the thinness.
The approach is similar to the US National Institute of Mental Health’s Research Domain Criteria, which studies the psychological, biological and genetic traits of mental illness to understand varying degrees of dysfunction, rather than focusing on specific diagnostic labels.
Chief executive of the InsideOut Institute for eating disorders Dr Sarah Maguire said it was premature to throw out the diagnostic framework and classifications for eating disorders.
Dr Maguire said the ‘underweight’ criterion “does cause problems, but there are also powerful reasons for maintaining it”.
“A hallmark of anorexia is that obsessive drive for thinness and weight loss. We can’t eliminate it completely,» she said.
Dr Maguire hoped current research into underlying genetic biomarkers for anorexia, as well as bulimia and binge-eating disorders would help improve diagnosis in the future.
“But we are not there yet,» she said. «As sector, we have not reached a consensus about the best way to tackle the classifications of eating disorders.
Kate Aubusson is Health Editor of The Sydney Morning Herald.