The Lancet diabetes and endocrinology global commission now recommends other measures of excess body fat and ill health be used to diagnose obesity.
The clinical definition of obesity is set to shift, as experts with The Lancet’s diabetes and endocrinology global commission – backed by 75 medical organisations – call for doctors to take a more nuanced approach to diagnosis.
While some Australian obesity experts say it will overhaul the current process of diagnosing and treating obesity, others say that it just gives language to what doctors are already likely doing.
What are the changes?
In its paper published today, the commission argued for two major changes.
The first is that BMI should no longer be used in isolation to diagnose obesity.
Under the proposed new model, obesity would be diagnosed one of three ways: direct body fat measurement, BMI and one anthropometric measure or two anthropometric criteria regardless of BMI.
The anthropometric measures include waist circumference, waist-to-hip ratio and waist-to-height ratio, while the direct body fat measures include bone densitometry scan or DEXA.
In cases where BMI exceeds 40, however, the researchers said excess body fat could be pragmatically assumed.
The second change would see obesity split into two categories, pre-clinical and clinical.
The pre-clinical label would be for people who have excess adiposity but preserved organ and tissue function.
A diagnosis of clinical obesity, meanwhile, requires evidence of reduced organ function due to obesity and/or significant, age-adjusted limitations of day-to-day activities that reflect the specific impact of obesity.
There are 18 of these diagnostic criteria for adults, including chronic or recurrent atrial fibrillation, sleep apnoeas, raised arterial blood pressure, PCOS, knee or hip pain with joint stiffness, lower limb lymphedema, and chronic fatigue.
Children and adolescents have a separate set of 13 diagnostic criteria, which omits some of the adult measures related to cardiovascular health but includes additional criteria on musculoskeletal health.
Where pre-clinical obesity is classified as a state that confers an increased risk of several diseases – i.e. a risk factor – clinical obesity is classified as a chronic, systemic illness.
What do the changes mean for general practice?
Endocrinologist Professor Priya Sumithran, who was one of the 58 commissioners involved in writing the report, said the benefit of distinguishing between clinical and pre-clinical obesity comes in being able to prioritise treatment access for people whose health is already being impacted by obesity.
“Obesity is so variable in how it affects the individual,” she told The Medical Republic.
“Some people have preserved health, some people have high risk of future ill-health and some people have ill-health right now.
“This provides a framework to identify that and then use appropriate management strategies for the individual depending on their needs.”
It’s something she felt GPs were likely already doing to some extent.
“In terms of assessing the health of patients – not just looking at their body mass index – and managing them according to their health needs, that’s something that practitioners are already doing,” Professor Sumithran said.
“But I think that the commission’s definitions and diagnostic criteria provide a framework and terminology to standardise how we do that.”
Fellow commission member Professor John Dixon, a clinical obesity researcher with Baker Heart and Diabetes Institute, said the proposed model would “overhaul” existing ideas about diagnosing and treating obesity.
“The aim is to facilitate individualised assessment and care of people with obesity while preserving resources for those … people who are under-diagnosed and people who are adequately diagnosed,” he said.
Asked what GPs can do to change their day-to-day practice, Professor Dixon said there was an opportunity to start taking a granular approach to deciding whether a patient has obesity as a disease or a risk factor.
“Is there excessive fat, is there a pre-obesity condition, is there a clinical obesity condition – I think those areas are going to be very important,” he said.
“Clinical obesity needs to be put down as a chronic disease in the patient’s list – it shouldn’t be sitting [under] heart failure or diabetes if, in fact, it’s a disease in itself.”
He predicted that this may meet with resistance in some quarters.
“We need to address stigma among our healthcare practitioners from every aspect, because patients see it and it puts them off and it damages them,” Professor Dixon said.
“We have to educate … many health practitioners actually don’t think it’s a disease.
“They like to think that it’s their [patient’s] fault and so forth.
“They’re going to take time to adjust to this … and we’re going to have to do a lot of work in Australia to actually change those views and destigmatise this condition so that we can treat it logically, like we do any other chronic disease.”
Why make these recommendations?
Consensus among all commissioners was higher than 90% across all 87 definitions, criteria and recommendations, and was unanimous for more than half of those.
But it didn’t start that way; at the outset, the expert committee was split between viewing obesity as a disease or a risk factor.
Commission chair Professor Francesco Rubino said the sticking point had been the all-or-nothing implication of the question.
“Any blanket definition of obesity in this context, whether we consider obesity only as a risk factor or as a disease, creates a distortion with a lot of negative implications,” he said.
One example he gave was a patient who had a heart impairment, lung dysfunction and heart failure related to obesity, but no diabetes.
In many countries, Professor Rubino said, the presence of obesity alone would not be sufficient to trigger insurance coverage.
If obesity was defined only as a risk factor, the absence of a disease diagnosis may affect that patient’s access to surgery, medication or other forms of appropriate care.
On the other end of the spectrum, if obesity was only ever considered a disease, it would capture patients who have no signs or symptoms of ongoing illness.
“A disease diagnosis is not about when and if – it’s about here and now,” Professor Rubino said.
“In this case, we risk overdiagnosis … and potentially unwarranted use of surgical operations, drugs and therapies.”
Whether obesity is a disease or not also changes factors like urgency of care and the level of acceptable risk in a treatment option.
Where to next?
While the commission’s paper has the endorsement of 76 professional health and non-profit organisations across the globe, it has not yet been discussed with any individual government or health system.
University of Sydney paediatrician and weight management researcher Professor Louise Baur, who also sat on the commission, said there were a number of further studies needed to clarify the prevalence of the two sub-types of obesity.
It will take time, she said, for discussions with government about whether and how the new model could be implemented and what interventions may exist on a public health level.
“Our reframing essentially acknowledges the nuanced reality of obesity and allows for patient for personal care of people with clinical obesity,” she said.
