Millions of people could be spared misdiagnosed obesity under a new combined measure of BMI and waist size.
The framework combines BMI with waist circumference or waist-to-height ratio, addressing the inability of BMI to distinguish fat from muscle.
Among more than 844,000 people across China, Spain, the United Kingdom and the United States, the combined measure identified obesity in 9% of cases missed by BMI and prevented mislabeling 3% of individuals as obese.
The concept of preclinical obesity describes excess weight that does not require immediate treatment; 77% to 91% of such cases did not progress to clinical obesity over ten years.
Clinical obesity carried a 69% higher mortality risk, while preclinical obesity showed a 19% increased risk compared with people without excess fat.
With GLP-1 drugs available, the finer diagnostic detail can inform treatment choices, dosing and long-term management.
The results support replacing BMI-only assessments with a multi-measure approach similar to standards used for other medical conditions.