CKM outcomes in HK after reclassifying obesity by the Lancet Commission’s definition

In an observational study of two community-based cohorts in Hong Kong, 6.7 percent of individuals with BMI ≥25 kg/m² were reclassified as nonobese after applying the Lancet Commission’s definition of obesity. Individuals with clinical obesity had the highest risk of adverse cardiovascular-kidney-metabolic (CKM) outcomes, while those reclassified as nonobese had an intermediate risk.

New definition of obesity: Beyond BMI alone

Previously, overweight and obesity were classified based on BMI alone, with 25 kg/m² applied as cut-off for obesity in Asians. [www.chp.gov.hk/en/resources/e_health_topics/pdfwav_11012.html] The Lancet Commission’s January 2025 report redefined obesity as excess and abnormal adiposity measured by one of the following methods:

“Introduction of the Lancet Commission’s definition of obesity will likely change the prevalence of obesity,” wrote the Hong Kong study’s author, Dr David Lui of the Department of Medicine, University of Hong Kong. “More importantly, the long-term outcomes of those who are reclassified as nonobese have not been reported.” [PLoS Med 2026;23:e1004749]

Hence, Lui and colleagues conducted an observational study of two representative Hong Kong Chinese community-based cohorts, including N-CRISPS (n=3,258; mean age, 49 years) to assess the new prevalence of obesity using cross-sectional analysis, and CRISPS (n=2,900; mean age, 46 years) to investigate long-term CKM outcomes.

Results showed that 6.7 percent of individuals with BMI ≥25.0 kg/m² were reclassified as nonobese under the Lancet Commission’s definition. This proportion is “small but not negligible”, commented Lui.  

“From the perspective of public health, BMI still serves as an important index to alert the general public to the need of maintaining optimal BMI for health,” remarked Lui.

CKM outcomes by the new definition

The Lancet Commission introduced two new categories of obesity:

• Preclinical obesity (ie, preserved function of other tissues and organs);
• Clinical obesity (ie, evidence of obesity-related organ dysfunction or significant, age-adjusted limitations of day-to-day activities). [Lancet Diabetes Endocrinol 2025;13:221-262]

CKM outcomes, including incident diabetes, cardiovascular disease, cancer, kidney outcomes, and all-cause mortality, were evaluated in the Hong Kong study over a median follow-up of >20 years. [PLoS Med 2026;23:e1004749]

“Across the range of CKM outcomes, we observed a graded increase in risk of each outcome from normal/underweight, overweight, BMI ≥25 kg/m² without confirmed excess adiposity, and preclinical obesity to clinical obesity,” reported Lui.

Of note, clinical obesity by the revised definition was associated with the highest risk of CKM outcomes. The group with BMI ≥25 kg/m² without confirmed excess adiposity consistently had intermediate risk of all CKM outcomes.  

“Identifying individuals with clinical obesity can help prioritize interventions for this high-risk population,” commented Lui. “Nonetheless, we should not ignore those who are reclassified as nonobese under the Lancet Commission’s definition, as these individuals still have a higher risk of adverse long-term health impacts than those with normal BMI.”