A decade-long study involving over 844,000 participants across China, Spain, the U.K., and the U.S. indicates that a new framework for assessing obesity, which combines Body Mass Index (BMI) with waist circumference or waist-to-height ratio, offers a more accurate evaluation than BMI alone.
The research, published in the journal Nature, found that using BMI exclusively resulted in nearly 9% of individuals with obesity being misdiagnosed, while 3% were incorrectly identified as having obesity when their weight was not a significant health concern. These figures translate to millions of misclassified individuals globally, according to Francesco Rubino, a lead researcher at King's College London.
For years, health professionals have recognized BMI's limitations, as it cannot differentiate between muscle mass and body fat. The new framework aims to provide a more nuanced understanding of an individual's health risks associated with excess weight.
Distinguishing Preclinical and Clinical Obesity
The study also supports a new classification system that distinguishes between "preclinical obesity" and "clinical obesity." Preclinical obesity refers to individuals with excess weight who may not require immediate medical intervention, while clinical obesity indicates a diagnosis that necessitates prompt treatment such as dietary changes, exercise, or medication.
Over a 10-year period, the study observed that approximately 77% to 91% of individuals classified with preclinical obesity did not progress to clinical obesity. However, those with clinical obesity faced a 69% higher risk of mortality compared to individuals without excess fat. For those with preclinical obesity, the mortality risk was 19% higher than those without excess fat.
Rubino emphasized that this distinction is crucial for healthcare providers to tailor treatment strategies effectively. "The scale of the problem with BMI is beyond what we imagined," Rubino stated. "We all know that BMI doesn’t represent health accurately. But the scale of the problem is concerning because of the number of people it misclassifies, by misdiagnosing in both directions."
The study's findings are particularly relevant given the increasing availability and effectiveness of obesity treatments like GLP-1 medications. Precise diagnostic tools are essential for guiding treatment decisions, including medication adherence, dosage, and counseling patients on managing side effects.
The researchers suggest that the comprehensive approach, incorporating multiple measurements, aligns with diagnostic standards used for other medical conditions and provides robust evidence to move away from sole reliance on BMI for obesity assessment.