New research suggests doctors may misdiagnose childhood obesity

The Lancet Commission's definition of clinical obesity, which requires evidence of health complications beyond body mass index, sharply reduces the rate of affected children.

The new definition of obesity goes beyond BMI and takes into account health impacts

Murdoch Children's Research Institute paediatrician, Dr Daniel Longmore, presents a new definition of global childhood obesity from the Murdoch Children's Research Institute, which goes beyond BMI. Longmore explains how the new definition takes into account critical health impacts.

A new global definition of childhood obesity is reshaping how clinicians assess the health of young people by looking away from traditional measurements of body mass index (BMI) to focus on real physiological effects.

According to research by the Murdoch Children's Research Institute in Australia, only 2.1% to 4.9% of children and adolescents qualify as clinically obese under the revised standard, compared to 7% to 10.8% in standard BMI calculations.

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"There's an appetite for understanding how body fat affects health," says Longmore. "BMI really only measures size. So it doesn't really have a way of telling whether it's good or bad."

The traditional BMI measurement calculates people's weight relative to their height.

While the rate of clinical obesity is significantly lower in young adults, it increases with age, reaching 52 percent among adults aged 65 to 74 years with an accumulation of chronic conditions. (iStock)

The new definition, created by an international panel of medical experts published by The Lancet medical journal, requires evidence of excess body fat and associated health problems or limitations in daily activities.

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These indicators can range from high blood pressure and abnormal blood sugar to impaired mobility or poor sleep.

Longmore noted that many children defined as obese by BMI criteria are active, sleep well, go to school and are otherwise healthy.

The new diagnostic model formalizes what many pediatricians already do by assessing blood pressure, blood sugar, sleep and physical activity in addition to size. (iStock)

"I think this definition really captures what people were doing in actual clinical practice," Longmore said.

While clinical obesity appears to be significantly less prevalent in young adults under the new model, this trajectory reverses dramatically later in life.

The study, which followed nearly 800,000 people over their lifetimes, found that rates of clinical obesity increased into adulthood.

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Among adults aged 65 to 74, the rate of clinical obesity reached 52 percent, as health problems associated with excess body fat became more common with age.

The findings come at a time when prescription weight-loss drugs, particularly GLP-1 receptor agonists, are growing in popularity.

Many children classified as obese by traditional BMI standards are fit, active, and healthy with no secondary medical complications. (iStock)

However, Longmore cautioned that the study's data set reflects pre-GLP-1 records, making the long-term effect of these treatments an open area for future study.

"This is really just the beginning of understanding what this new diagnostic entity means, and we really need more research," said Longmore, emphasizing that although this definition modifies clinical diagnoses, early health interventions and lifestyle prevention are still critical for at-risk children.

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