# The impact of the Lancet Commission definition of obesity on its prevalence and implications on long-term cardiovascular-kidney-metabolic outcomes in East Asians: Observational study of two community-based cohorts

## TL;DR

A new obesity definition reduces obesity prevalence in Chinese populations and affects long-term health risks differently based on additional body measurements.

## Contribution

This study evaluates the impact of the Lancet Commission's updated obesity definition on prevalence and health outcomes in East Asians.

## Key findings

- Applying the Lancet Commission definition reduced obesity prevalence from 44.5% to 33.8% in men and from 26.7% to 24.1% in women.
- Individuals reclassified as non-obese under the new definition had intermediate cardiometabolic risks between preclinical obesity and overweight categories.
- Clinical obesity, as per the new criteria, was associated with the highest risk of adverse cardiovascular-kidney-metabolic outcomes.

## Abstract

The Lancet Commission proposed an update in January 2025 on the definition of obesity which requires at least one anthropometric measurement in addition to body mass index (BMI) to confirm excess adiposity. Also, the presence of obesity-related organ dysfunction is used to differentiate between clinical and pre-clinical obesity. We evaluated how applying the Lancet Commission proposed definition of obesity, which required an additional anthropometric measurement to verify excess adiposity, would affect its prevalence, and its implications on the cardiovascular-kidney-metabolic health.

We used two representative Chinese community-based cohorts and compared five categories of participants with (i) clinical obesity, (ii) preclinical obesity, (iii) BMI ≥25 kg/m2 without confirmed excess adiposity, (iv) overweight and (v) normal/underweight in the cross-sectional cohort for cardiometabolic risk profiles and in the longitudinal cohort for long-term cardiovascular-kidney-metabolic outcomes. In the cross-sectional cohort, the prevalence of obesity was 44.5% in men and 26.7% in women defined by the Asian BMI cutoff of ≥25.0 kg/m2, and decreased to 33.8% and 24.1%, respectively, using the Lancet Commission definition (BMI ≥ 25.0 kg/m2 and elevated waist circumference). Applying the Lancet Commission definition would reclassify a portion of individuals who are initially classified as having obesity based on BMI criteria alone (BMI ≥ 25.0 kg/m2) but with normal waist circumference to be non-obese (category iii). The individuals falling into category iii had an adverse cardiometabolic health profile which was intermediate among the five categories regarding insulin resistance and visceral adiposity (falling in between categories ii and iv). In the longitudinal cohort with a median follow-up of over 20 years, people with clinical obesity had the poorest cardiovascular-kidney-metabolic outcomes including all-cause mortality, whereas those reclassified as non-obese had an intermediate risk of adverse cardiovascular-kidney-metabolic outcomes among the five categories. The main limitation of the study was that all participants were Chinese and findings might not apply to other ethnic groups.

Adoption of the Lancet Commission definition would classify a small proportion of individuals with BMI of ≥25.0 kg/m2 as non-obese. People with clinical obesity identified by the revised criteria had the highest risks of cardiovascular-kidney-metabolic outcomes including all-cause mortality, whereas individuals reclassified as non-obese had intermediate risks of cardiovascular-kidney-metabolic outcomes between those in pre-clinical obesity and overweight categories.

The Lancet Commission proposed an update in January 2025 on the definition of obesity which requires at least one anthropometric measurement in addition to body mass index (BMI) to confirm excess adiposity.

Only two population-based cross-sectional studies, one on a United States cohort and one in the United Arab Emirates, have evaluated the impact of applying the Lancet Commission definitions on the prevalence of obesity, but these did not report long-term outcomes.

This study used two representative Hong Kong Chinese community-based cohorts to analyse (i) the cardiometabolic risk profile of the participants with clinical/pre-clinical obesity and those who would be reclassified as non-obese based on the Lancet Commission definition cross-sectionally, and (ii) the long-term cardiovascular-kidney-metabolic outcomes over a median follow-up of over 20 years

Application of the Lancet Commission definition led to reclassification into non-obese for 6.7% of the cohort who would otherwise have been diagnosed to have obesity based on BMI cut-off alone; these people were in the intermediate range of the spectrum of BMI and adiposity

Clinical obesity presents the highest risk of adverse cardiovascular-kidney-metabolic outcomes, while people reclassified as non-obese still had more adverse long-term health impacts than those with normal body weight

Compared to BMI-alone criteria, the Lancet Commission definition identifies people with clinical obesity to maximise benefits of timely intervention, but people who were diagnosed to have obesity based on BMI cut-off alone but reclassified as non-obese under the Lancet Commission definition still had higher risk of adverse outcomes than those with normal BMI.

For public health, BMI is still an important index to raise awareness to prevent obesity.

The main limitations of the study were that all participants were Chinese and the limited consideration of social and environmental determinants in relation to the various cardiovascular-kidney-metabolic outcomes.

In an observational study, David Lui and colleagues investigate the effect of a new obesity definition on the classification of individuals as overweight in two Chinese cohorts.