Using new obesity diagnosis standard research, a recent international study reveals that relying solely on the Body Mass Index (BMI)βcalculated using height and weightβmakes it difficult to accurately screen for obesity and associated health risks.
Joint research teams, including institutions from King’s College London and Huazhong University of Science and Technology, published findings in the international journal Nature. They analyzed physical measurement data and health records from 844,108 adults across China, the UK, the US, and Spain to validate the updated obesity diagnosis criteria.
The evaluated criteria were initially proposed in January of last year by the ‘Lancet Diabetes & Endocrinology Commission,’ which comprised 58 experts from countries including South Korea, the UK, the US, China, Japan, and Australia. Professor Soo Lim of Seoul National University Bundang Hospital participated from South Korea, while Professor Francesco Rubino of King’s College London led the commission and joined the validation research team.
BMI divides weight by height squared. In South Korea, a BMI between 23 and 25 is classified as overweight (pre-obesity), while 25 or higher is classified as obesity. Meanwhile, general World Health Organization (WHO) adult standards are 25 to 30 for overweight and 30 or higher for obesity.
However, BMI alone fails to distinguish muscle-to-fat ratios or the specific location of accumulated fat. The new diagnostic approach integrates BMI with waist circumference and the waist-to-height ratio (WHtR) to better evaluate fat accumulation. Even if individuals fall into the overweight category under national BMI thresholds, they are classified as obese if both their waist circumference and WHtR meet obesity standards.
The updated criteria also categorize types of obesity based on health status. If excessive fat accumulation causes functional impairments in organs such as the cardiovascular, respiratory, metabolic, liver, or kidney systems, or significantly limits daily life, it is diagnosed as ‘clinical obesity.’ If these issues are absent, it is classified as ‘pre-clinical obesity,’ effectively distinguishing the actual impact of obesity on health rather than just the degree of adiposity.
When applying the new criteria, the proportion of individuals classified as obese increased. Across the studied populations, 5.2% to 8.6% of people who were previously classified merely as overweight by BMI alone shifted into the obesity category. Conversely, 1.2% to 3.1% of individuals previously labeled obese by BMI were excluded under the new standards.
Consequently, the overall percentage of people categorized as obese rose: China’s study group increased from 17.8% to 21.3%, the UK from 24% to 27.3%, the US from 42.5% to 48.1%, and Spain from 18.7% to 26.1%.
Mortality risks also varied among those classified as obese. Analyzing data from three countries excluding the US, the mortality risk for the clinical obesity group was 69% higherβand for the pre-clinical obesity group, 19% higherβcompared to individuals who were neither obese nor had impaired organ function.
Researchers suggest this new obesity diagnosis system can help determine patient treatment needs and priorities while improving the efficient allocation of medical resources. Data collected from South Korea was not included in this particular study.
