New Obesity Criteria Classify Fewer Australian Children as Clinically Obese
09 Oct 2026
A large international study has found that the number of children classified as having clinical obesity drops when doctors assess the effects of excess body fat on health, rather than using body mass index (BMI) alone.
The Murdoch Children's Research Institute analysed health data from 786,557 people across several countries, including Australia. The study compared the newer global definition of clinical obesity with traditional BMI-based classifications.
Under the new criteria, clinical obesity affected between 2.1% and 4.9% of children and adolescents. By comparison, BMI-based measures classified between 7% and 10.8% as obese.
The newer approach considers whether excess body fat is linked to health problems or difficulties with everyday activities. It aims to help clinicians distinguish between excess body fat and obesity that is already affecting a person's health.
Lead researcher Dr Danielle Longmore said the definition could help healthcare professionals make better decisions about treatment. The findings could also help guide decisions about obesity medications and nutrition plans.
However, Australian GPs have stressed that children who do not yet show health complications should not be overlooked.
Dr Mark Mellor, a GP with a special interest in obesity management, said assessments should reflect each child's health needs. He said children with early-stage obesity may still face future health risks, even if no measurable problems are present at the time of assessment.
Children whose obesity is already affecting their health should also have access to appropriate treatment, he said.
Dr Terri-Lynne South, Chair of RACGP Specific Interests Obesity, raised concerns that the new findings could lead to less support for children who have excess body fat but no current complications.
She said early action can help improve a child's long-term health. Waiting until physical problems develop could mean the effects of obesity are already becoming more serious.
The study also found that clinical obesity became more common with age. Among adults aged 65–74, the rate reached 52%. Clinical obesity was more common among men during early and middle adulthood, while women had higher rates later in life.
Dr South said obesity often becomes more difficult to manage over time, making early support particularly important for young people who may face health risks over many years.
She emphasised that the absence of current complications should not stop GPs from offering help. Children with early-stage obesity may benefit from family-based support that encourages healthier daily routines and lifestyle choices.
The goal is to address risks early and help prevent obesity from progressing to a stage where it affects health and daily functioning.
New Obesity Criteria Classify Fewer Australian Children as Clinically Obese
Source: Murdoch Children's Research Institute study published in eClinicalMedicine, part of The Lancet group. Read the research.