The impact of new obesity definitions on prevalence and health outcomes

Recently, the European Association for the Study of Obesity (EASO) andLancet Diabetes & Endocrinologyhave proposed new frameworks for diagnosing obesity. This study aimed to examine the association between different defined obesity subgroups and clinical outcomes.

Using the UK Biobank, we enrolled individuals based on updated diagnostic criteria and described the variations in obesity prevalence under different definitions. We then calculated the proportion eligible for treatment. Furthermore, we compared the spectrums of obesity-related dysfunctions across definitions and conducted stratified analyses by sex and ethnicity. Finally, we assessed the associations between various obesity subtypes and the incidence of type 2 diabetes (T2D), cardiovascular events, end-stage renal disease (ESRD), and all-cause mortality with adjusted Cox proportional hazards models.

Among 498,353 subjects (median age 58 [50, 63] years), 54.4% were female. The EASO and Lancet frameworks identified 29.6% and 63.4% of participants, respectively, as having obesity-representing increases of 4.8% and 38.6% over the BMI-based WHO definition. Hypertension, metabolic disorders, and musculoskeletal conditions were the most prevalent obesity-related dysfunctions overall, with variations by sex and ethnicity, particularly elevated among Asian populations. Notably, overweight as defined by EASO or Lancet criteria was not consistently a risk factor, in some context appeared protective. However, clinical obesity under the Lancet criteria conveyed the highest risk of progression to severe outcomes among all obesity subtypes, with significantly elevated hazards for T2D (HR = 12.33, 95% CI: 11.74-12.96), cardiovascular events (HR = 4.02, 95% CI: 3.89-4.16), ESRD (HR = 7.13, 95% CI: 6.11-8.33), and all-cause mortality (HR = 3.07, 95% CI: 2.99-3.15), exceeding risks associated with EASO- and WHO-defined obesity.

New obesity criteria significantly increased diagnosed prevalence, especially among Asians. Notably, overweight by EASO or Lancet standards does not uniformly raise health risks. Consequently, the choice of diagnostic framework directly shapes risk stratification and informs personalized treatment strategies that should address body composition beyond weight alone.