King's College London study in Nature: BMI missed risk in 5–9% of 844 thousand adults

Researchers led by King's College London have published in Nature the results of an international project covering over 844 thousand adults from the United Kingdom, the United States, Spain and China, reports portal.abczdrowie.pl portal.abczdrowie.plportal.abczdrowie.plportal.abczdrowie.plOpen source ↗. The analysis shows that body mass index (BMI), the ratio of weight to height, can be misleading when assessing the health effects of excess fat.

Why BMI alone falls short

For decades a BMI of 30 and above has been classified as obesity. The index does not distinguish muscle mass from fat mass, does not show where fat accumulates, and does not check whether visceral fat has already begun to damage the heart, joints or kidneys. Two people with the same BMI can therefore be in very different medical situations.

Prof. Francesco Rubino, one of the authors, stated that BMI alone does not tell whether a person is already ill or only at risk of illness, nor what care is needed. In his words, this exposes people to both insufficient and excessive treatment.

In early 2025 an international commission appointed by The Lancet Diabetes & Endocrinology proposed moving away from BMI as the sole measure. It recommended a comprehensive assessment that includes waist circumference, especially relative to height, and a check of internal organ function portal.abczdrowie.plportal.abczdrowie.plportal.abczdrowie.plOpen source ↗. The new approach distinguishes two forms. In the clinical form, excess fat has become an active disease process that burdens the circulatory system, impairs breathing, causes metabolic disorders or degrades the musculoskeletal system. In the preclinical form, the risk is elevated, but the organs still work normally and no lasting damage has occurred.

What the data show

The researchers compared earlier diagnoses with the new model. In about 5–9 percent of patients, BMI missed a real risk that more precise body measurements detected, while in 1–3 percent of people obesity was diagnosed although waist circumference raised no concerns. According to the authors, only combining weight with waist circumference accurately identified people at risk of premature death.

The clinical form affected 23 to 31 percent of those diagnosed and was linked to a 69 percent higher probability of death from any cause compared with healthy peers. In the preclinical variant this risk rose by 19 percent, and 77 to 91 percent of patients did not develop full-blown disease over a decade of observation.

The authors conclude that treatment should not be uniform. Patients with organ changes may need prompt pharmacotherapy, while in the preclinical phase early changes of habits and lifestyle may be equally effective portal.abczdrowie.plportal.abczdrowie.plportal.abczdrowie.plOpen source ↗.