Health experts are calling for an overhaul of the way obesity is diagnosed internationally.

Doctors and health researchers say that relying solely on a person’s body Mass Index (BMI) to diagnose obesity is unreliable. 

University of Sydney Professor Louise Baur said a person’s BMI did not always provide the full picture of their weight.

“People who are muscly such as athletes might have a high BMI but not high body fat,” Baur said.

Dozens of international experts are calling for additional testing to diagnose obesity, like measuring someone’s waist circumference.

“[If there’s] extra fat around the middle…That’s where all your vital organs are, [it’s] pushing up on your heart and your lungs,” Monash University professor Wendy Brown said.

“We should be treating it like any other disease – without judgement.” 

Relying on BMI also means obesity could be underdiagnosed. 

Instead, experts from Lancet Diabetes & Endocrinology have identified 18 health problems that would mean someone with excess body fat could be diagnosed with obesity.

The issues include breathlessness and wheezing, sleep apnoea, severe knee or hip pain and heart failure. 

“It provides clinicians with a clear picture of what they need to assess what symptoms they need to look for,” Professor Francesco from Rubino Kings College in London said. 

There are still questions about equitable access to treatments like weight loss surgery, medications and lifestyle programs once a clear diagnosis has been made.

“We can’t expect people to pay for this out of their own pocket when it’s such a significant disease,” Baur said.

One-third of Australian adults are affected by obesity.