An international study published in Nature analyzed health data from over 844,000 adults across China, the United Kingdom, the United States, and Spain to propose diagnosing obesity using waist measurements alongside the body mass index.
The research demonstrates that relying solely on the body mass index, commonly known as BMI, both overestimates and underestimates obesity rates across diverse populations. Investigators examined data from 844,108 adults to see whether a framework proposed in January 2025 by a commission in The Lancet Diabetes & Endocrinology offers a more precise way to assess health outcomes.
“The people with obesity, like everyone else, deserve care tailored to their needs: neither less nor more,” said Rubino, in a press release reported by Euronews.com.
EL PAÍS said that incorporating waist circumference and waist-to-height ratios changed the condition's prevalence. In Spain, the percentage of individuals cataloged with obesity shifted from 18.7% to 26.1%, representing a relative increase of nearly 40%.
Global Data Reveals Misclassification Risks
El Mundo detailed that combining additional physical metrics with traditional BMI measurements improves detection rates between 3.3% and 7.4%.
20Minutos reported that the diagnostic framework operates in two distinct steps. First, clinicians combine BMI with the circumference of the waist and the waist-to-height ratio to confirm excessive body fat. Second, they differentiate between active disease where organ function is impaired and preclinical states where risks are elevated but organ function remains preserved.
Data from the cohort study showed that clinical obesity accounted for 23% to 31% of all identified cases. The overall population prevalence ranged from 5.6% to 10.9% across the four participating nations.
La Vanguardia highlighted that the two distinct categories correspond to substantially different mortality risks over a ten-year period. Clinical obesity is linked to a markedly higher risk of death from any cause, whereas preclinical obesity carries a much more moderate increase in risk.
The vast majority of individuals classified with preclinical obesity at the start of the study did not progress to the clinical form over a decade. El Mundo specified that in Catalonia, approximately 77% of individuals with preclinical obesity did not progress, compared to roughly 91% in the United Kingdom cohort.
“The body mass index alone cannot tell us if someone is already sick or at risk of getting sick, or what care they need, leaving people vulnerable to both undertreatment and overtreatment,” Rubino said.
“The marked differences in prognosis between clinical and preclinical obesity, observed consistently across countries and ethnic groups, support the global adoption of the new framework to improve obesity care and policies worldwide,” said An Pan, first author of the study from Huazhong University of Science and Technology in Wuhan, China.
Experts Call for More Evidence on Treatment Outcomes
EL PAÍS reported that Diego Bellido Guerrero, president of the Spanish Society for Obesity, known as SEEDO, described the research as solid while noting it does not explicitly demonstrate that adopting this classification actively improves treatment outcomes or reduces complications. Bellido Guerrero maintained that universal adoption requires further evidence.
El Mundo said that the scientific director of the Biobank at the Girona Biomedical Research Institute and Ciberobn coordinator emphasized that location of fat accumulation matters more than a simple number on a scale.
In Plain English: The Clinical Takeaway
- Two Distinct Stages: The framework separates preclinical obesity, where health risks are higher but organ function remains normal, from clinical obesity, where organ function is already impaired.
| Metric Category | Traditional BMI Standard | Proposed Dual Framework |
|---|---|---|
| Core Measurements | Height and weight only | Weight, height, and waist circumference |
| Misclassification Rate | Overestimates or underestimates up to 8.6% of cases | Reduces classification errors using abdominal ratios |
| Diagnostic Categorization | Single threshold for all elevated weights | Differentiates preclinical risk from clinical organ dysfunction |
Waist Measurements Reduce Diagnosis Errors
The research team concluded that utilizing waist measurements alongside height and weight limits both underdiagnosis and overdiagnosis.
References
- Rubino, F., et al. (2026). Clinical and preclinical obesity definitions across international cohorts. Nature.
- The Lancet Diabetes & Endocrinology Commission. (2025). A new framework for the diagnosis of clinical obesity. The Lancet.
