A new approach to defining obesity, reported by New Scientist, could transform how healthcare systems worldwide treat millions of people living with the condition. Researchers are advocating for a more nuanced classification system that goes beyond the traditional reliance on body mass index (BMI) to assess and treat obesity.
Obesity, as defined by the World Health Organization (WHO), involves excessive body fat that poses a health risk. Traditionally, BMI—a simple measure of weight relative to height—has been used to determine whether a person is obese. A BMI above 30 is considered obese, while a BMI between 18.5 and 24.9 is classified as healthy. However, BMI has long been criticized for its limitations.
“With BMI, we don’t know if that ‘excess’ weight is due to excess body fat, stronger muscle mass, or bone mass,” said Francesco Rubino from King’s College London, who led this groundbreaking review.
Rubino and his team propose introducing two categories for obesity: preclinical obesity and clinical obesity. Both involve excess body fat, but they differ in terms of health impact. Clinical obesity would be defined by the presence of symptoms caused by excess fat, such as heart problems, breathing difficulties, or challenges in performing daily activities. Preclinical obesity, on the other hand, would indicate an increased risk of developing such symptoms in the future.
“This is akin to how prediabetes works,” Rubino explained, referencing the condition where blood sugar levels are elevated but not yet at the level for a diabetes diagnosis.
A More Comprehensive Assessment
The proposed changes would shift the focus from BMI alone to a combination of methods for evaluating obesity. Direct measurements of body fat using waist circumference or X-ray scans would complement BMI. Additionally, blood tests would assess organ health, while healthcare professionals would consider symptoms reported by patients. For those with a BMI above 40, obesity would automatically be assumed due to the high likelihood of excess fat.
Steven Heymsfield from Louisiana State University emphasized that this approach accounts for individual differences. “No two people respond the same way to excess body fat. This is impacted by race, ethnicity, age, diet, and genetics,” he said.
If adopted, the new definitions could lead to more tailored advice and treatment. For example, those with preclinical obesity might only require lifestyle adjustments and regular health monitoring, whereas those with clinical obesity would likely need medication or surgery.
“It would allow us to more appropriately triage people to the right care,” said Adrian Brown from University College London.
Addressing Stigma and Misconceptions
The revised definitions have already been endorsed by 76 health organizations worldwide and could play a significant role in reducing the stigma surrounding obesity. “Defining obesity in a more nuanced way shows it is a disease in its own right,” said Laura Gray from the University of Sheffield. “It isn’t just a consequence of behavioral factors; there are numerous risk factors—environmental, psychological, and genetic.”
Rubino and his colleagues hope this redefinition will not only improve treatment outcomes but also promote a more compassionate understanding of obesity as a medical condition rather than a simple matter of willpower or lifestyle.
