Newshot Chinese Scientists' Latest Study: BMI Alone Is Not Enough to Diagnose Obesity; 5.2–8.6% Underestimated and 1.2–3.1% Overestimated
IT Home, November 13: According to a report by Xinhua News Agency yesterday, a study completed by the team of Professor Pan An, dean of the School of Public Health at Huazhong University of Science and Technology, together with experts from multiple countries, was published in Nature on November 12.
Based on data from four large cohorts in China, the UK, the US, and Spain, covering more than 844,000 adults in total, the study systematically validated the refined obesity diagnostic framework proposed in 2025 by The Lancet Diabetes & Endocrinology Commission. The conclusion is clear: diagnosing obesity based on BMI alone will lead to a considerable proportion of missed diagnoses and misdiagnoses.
BMI has long been used as a core indicator for obesity screening, but it can only reflect the ratio of weight to height; it cannot distinguish whether the added weight comes from fat or muscle, nor can it determine whether fat has already caused damage to organ function.
In the study, Pan An pointed out that this "inherent defect" directly manifests in clinical practice as two types of errors: some people with excessive body fat who already have impaired organ function are missed because their BMI does not reach the obesity threshold; another group of people whose BMI exceeds the standard but whose body fat is not excessive are misjudged as obese.
Research data show that, compared with the refined framework, using BMI alone would cause 5.2% to 8.6% of participants to have their degree of obesity underestimated, while 1.2% to 3.1% would be overestimated. Co-author of the paper and professor at King's College London Francesco Rubino said that more accurately identifying and defining obesity cases can help improve patient outcomes.
The framework proposed by the Lancet Commission distinguishes people with excessive body fat into "clinical obesity" and "preclinical obesity." Clinical obesity requires the presence of organ function impairment or limitation of daily activities caused by obesity; preclinical obesity refers to a state in which body fat is excessive but organ function has not yet been impaired. Among people with excessive body fat, only 22.7% to 31.3% met the criteria for clinical obesity, while the majority of the rest were in the preclinical stage.
The health risks corresponding to the two states differ significantly. In follow-up tracking of more than 10 years, the all-cause mortality risk of people with preclinical obesity increased by 19% compared with healthy people, while the mortality risk of people with clinical obesity rose to 69%.
The study also found that about 77% to 91% of people with preclinical obesity did not progress to clinical obesity during the follow-up period, suggesting that intervention at the stage when organ function has not yet been impaired offers a window to block the progression of the disease.
The four-country cohort design adopted by the study allowed the conclusions to be cross-tested in different populations and healthcare systems.
IT Home note: A cohort study refers to a research design in which people are grouped according to whether they are exposed to a certain factor or different levels of exposure, and the occurrence of outcomes is tracked and observed; it is often used to evaluate the association between disease risk factors and outcomes.
Public information shows that Pan An is the only Chinese representative on the Lancet Commission, and the Chinese Obesity Definition and Evaluation Alliance (CODE), which his team led the establishment of, will advance precision prevention research on this basis.
Paper link: https://www.nature.com/articles/s41586-026-11237-5
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