New obesity diagnostic frameworks from EASO and Lancet significantly increased obesity prevalence compared to WHO BMI-based definitions, and clinical obesity under the Lancet criteria conveyed the highest risk of progression to severe outcomes among all obesity subtypes.
Key Findings
Results
The EASO and Lancet frameworks identified substantially more individuals as having obesity compared to the WHO BMI-based definition.
Among 498,353 UK Biobank subjects, the EASO framework identified 29.6% as having obesity, and the Lancet framework identified 63.4%.
The WHO BMI-based definition identified approximately 24.8% as obese (implied by the increases reported).
These represent increases of 4.8% and 38.6% over the BMI-based WHO definition, respectively.
Median participant age was 58 [50, 63] years; 54.4% were female.
Results
Clinical obesity under the Lancet criteria was associated with the highest risk of type 2 diabetes among all obesity subtypes.
HR for T2D = 12.33 (95% CI: 11.74–12.96) for Lancet-defined clinical obesity.
This hazard ratio exceeded risks associated with EASO- and WHO-defined obesity.
Associations were assessed using adjusted Cox proportional hazards models.
Lancet clinical obesity conveyed the highest risk of progression to severe outcomes among all obesity subtypes.
Results
Clinical obesity under the Lancet criteria was associated with significantly elevated risk of cardiovascular events.
HR for cardiovascular events = 4.02 (95% CI: 3.89–4.16) for Lancet-defined clinical obesity.
This exceeded risks associated with EASO- and WHO-defined obesity subtypes.
Analyses used adjusted Cox proportional hazards models.
Results
Clinical obesity under the Lancet criteria was associated with significantly elevated risk of end-stage renal disease (ESRD).
HR for ESRD = 7.13 (95% CI: 6.11–8.33) for Lancet-defined clinical obesity.
This risk exceeded that associated with EASO- and WHO-defined obesity.
ESRD was one of four major outcomes assessed alongside T2D, cardiovascular events, and all-cause mortality.
Results
Clinical obesity under the Lancet criteria was associated with significantly elevated all-cause mortality.
HR for all-cause mortality = 3.07 (95% CI: 2.99–3.15) for Lancet-defined clinical obesity.
This exceeded risks associated with EASO- and WHO-defined obesity subtypes.
Adjusted Cox proportional hazards models were used for all outcome analyses.
Results
Hypertension, metabolic disorders, and musculoskeletal conditions were the most prevalent obesity-related dysfunctions, with variations by sex and ethnicity.
These three condition categories were the most prevalent obesity-related dysfunctions overall.
Prevalence varied by sex and ethnicity.
Obesity-related dysfunctions were particularly elevated among Asian populations.
Stratified analyses by sex and ethnicity were conducted.
Results
Overweight as defined by EASO or Lancet criteria was not consistently a risk factor and in some contexts appeared protective.
Overweight under EASO or Lancet standards does not uniformly raise health risks.
In some contexts, overweight by these definitions appeared protective.
This finding was described as 'notable' by the authors.
This pattern contrasts with the high-risk profile of clinical obesity under the same frameworks.
Results
New obesity criteria significantly increased diagnosed prevalence especially among Asian populations.
The Lancet framework increased obesity prevalence by 38.6% over the WHO BMI-based definition.
The EASO framework increased obesity prevalence by 4.8% over the WHO BMI-based definition.
Increases were particularly notable among Asian populations.
The study used updated diagnostic criteria from both EASO and the Lancet Diabetes & Endocrinology framework.
Results
The choice of diagnostic framework directly shapes the proportion of individuals eligible for obesity treatment.
The study calculated the proportion eligible for treatment under each framework.
The Lancet framework's 63.4% obesity prevalence versus WHO's approximately 24.8% represents a dramatic difference in treatment-eligible populations.
The authors conclude that 'the choice of diagnostic framework directly shapes risk stratification and informs personalized treatment strategies.'
What This Means
This research suggests that how we define and diagnose obesity matters enormously for both how many people are classified as obese and what health risks they face. Using data from nearly 500,000 UK Biobank participants, this study compared three different obesity diagnostic systems: the traditional WHO system based on body mass index (BMI), a newer framework from the European Association for the Study of Obesity (EASO), and a framework proposed by the journal Lancet Diabetes & Endocrinology. The Lancet framework, which considers body composition and physical signs of obesity beyond just weight, classified 63.4% of participants as obese — more than double the WHO rate — while the EASO framework classified 29.6% as obese. Asian populations in particular saw large increases in their obesity diagnoses under the newer systems.
The study found that people classified as having 'clinical obesity' under the Lancet framework faced dramatically higher health risks than those classified under the WHO or EASO systems. For example, their risk of developing type 2 diabetes was more than 12 times higher, their risk of cardiovascular events was 4 times higher, their risk of end-stage kidney disease was over 7 times higher, and their risk of dying from any cause was 3 times higher — all compared to people without obesity. Interestingly, people classified only as 'overweight' under the EASO or Lancet criteria did not consistently face higher health risks and in some analyses even appeared to have lower risks than expected, a phenomenon sometimes called the 'obesity paradox.'
This research suggests that the way obesity is defined has real consequences for clinical care. A stricter, more comprehensive definition that goes beyond BMI to include measures of body composition and metabolic health identifies people at much higher risk of serious disease. At the same time, not everyone who meets a broader definition of obesity faces the same risks, which points to the need for personalized approaches to treatment that consider body composition rather than weight alone.
Qiao X, Yu D, Guo L, Pan Q. (2026). The impact of new obesity definitions on prevalence and health outcomes.. Diabetes research and clinical practice. https://doi.org/10.1016/j.diabres.2026.113522