New Obesity Definition Expands Risk Identification Beyond BMI Alone
Key Clinical Summary
- A new obesity definition integrating body mass index (BMI) with anthropometric measures increased obesity prevalence by 60% compared with BMI alone in a large US cohort.
- More than one-third of adults met criteria for clinical obesity, with prevalence exceeding 50% among those aged 70 years or older.
- Individuals with anthropometric-only obesity showed significantly higher risks of organ dysfunction and long-term cardiometabolic outcomes than those without obesity.
A revised obesity definition proposed by a recent Lancet Commission may significantly alter how obesity is identified in clinical and policy settings. Using data from the US-based All of Us cohort, investigators evaluated how integrating BMI with anthropometric measures affects obesity prevalence, risk stratification, and long-term health outcomes in adults.
Study Findings
This population-based longitudinal cohort study analyzed 301 026 adults enrolled in the All of Us program between 2017 and 2023, with a median follow-up of 4 years. Obesity was classified using both the traditional BMI-only definition and a new framework incorporating sex- and race-specific anthropometric thresholds.
Under the new definition, 68.6% of participants met criteria for obesity, compared with 42.9% using BMI alone, representing a 60% relative increase in prevalence. This rise was primarily driven by individuals with anthropometric-only obesity, defined as having at least 2 elevated anthropometric measures despite a BMI below the traditional obesity threshold.
Overall, 36.1% of the cohort had clinical obesity, characterized by organ dysfunction or physical limitation. Clinical obesity prevalence increased with age, affecting 54.4% of adults aged 70 years or older. Compared with individuals without obesity, odds ratios for organ dysfunction were 3.31 for those with BMI-plus-anthropometric obesity and 1.76 for those with anthropometric-only obesity.
Longitudinal analyses demonstrated that clinical obesity was strongly associated with adverse outcomes, including incident diabetes (adjusted hazard ratio [AHR], 6.11), cardiovascular events (AHR, 5.88), and all-cause mortality (AHR, 2.71). Preclinical obesity, defined by obesity without overt organ dysfunction, was also linked to increased risks of diabetes (AHR, 3.32) and cardiovascular events (AHR, 1.40), though to a lesser extent.
Clinical Implications
The findings suggest that reliance on BMI alone may substantially underestimate obesity-related risk, particularly among older adults and individuals with unfavorable body fat distribution. Integrating anthropometric measures allows for more precise identification of patients at elevated risk for organ dysfunction and long-term complications.
For clinicians, the new framework may prompt earlier recognition of at-risk individuals who would otherwise be classified as non-obese, potentially expanding eligibility for preventive interventions. For payers and managed care organizations, the marked increase in obesity prevalence could have significant implications for coverage decisions, resource allocation, and cost projections, particularly for obesity pharmacotherapy and chronic disease management.
The introduction of anthropometric-only and preclinical obesity as distinct categories also highlights gaps in evidence regarding optimal prevention, monitoring, and treatment strategies for these populations. Policymakers may need to consider how revised definitions affect public health surveillance, quality metrics, and health equity initiatives.
The authors note that adoption of the new definition “effectively stratified individuals at high risk of organ dysfunction and long-term complications,” while also revealing “critical gaps in knowledge regarding anthropometric-only obesity, preclinical obesity, and the shifting target population for obesity pharmacotherapy.” They emphasize that these groups represent high-priority areas for future research to inform evidence-based clinical care and policy decisions.
Conclusion
In this large US cohort, integrating BMI with anthropometric measures substantially increased obesity prevalence and improved risk stratification for adverse health outcomes. The findings underscore the potential clinical and public health impact of redefining obesity while highlighting the need for further research to guide care for newly identified at-risk populations.
Reference
Fourman LT, Awwad A, Gutiérrez-Sacristán A, et al. Implications of a new obesity definition among the All of Us Cohort. JAMA Netw Open. 2025;8(10):e2537619. doi:10.1001/jamanetworkopen.2025.37619
