Body mass index (BMI) has long been the most familiar way to describe obesity. However, BMI cannot distinguish body fat from muscle or indicate where fat is stored. It may therefore overlook differences in metabolic health among people with a similar body size. A nationwide study from the ChinaHEART cohort now suggests that assessing obesity-related health risks may require looking beyond BMI alone.
The research team analyzed data from 4,258,033 adults aged 35 to 75 years across all 31 provinces of the Chinese mainland. Participants entered the cohort between November 2014 and December 2023 and contributed more than 20 million person-years of follow-up. The researchers compared 15 indices reflecting body shape, visceral fat accumulation, and metabolic function.
Health outcomes were identified through linked mortality and hospitalization records. During a median follow-up of 4.9 years, the study documented 329,073 cardiovascular disease events, 71,925 diabetes events, 113,373 cancer events, and 38,674 chronic obstructive pulmonary disease events in corresponding analysis populations.
The study first examined how these obesity-related measures were associated with the risk of different chronic diseases. Higher values of most measures were generally associated with higher risks of cardiovascular disease and diabetes. In contrast, the relationships with cancer and chronic obstructive pulmonary disease were weaker and more complex, with some measures showing nonlinear or inverse associations. These contrasting patterns suggest that obesity-related health risks may differ substantially across diseases and may not be fully captured by a single measure.
The researchers then assessed how well each measure could distinguish individuals at different levels of disease risk. The results again showed clear differences across diseases. The Chinese visceral adiposity index (CVAI) showed relatively higher discrimination for cardiovascular disease, while the triglyceride-glucose index (TyG) showed relatively higher discrimination for diabetes. A body shape index (ABSI) showed relatively higher discrimination for chronic obstructive pulmonary disease. By contrast, all 15 measures had limited ability to discriminate overall cancer risk. Importantly, the absolute ability of these indices to distinguish future disease risk remained modest. Some composite measures combine body measurements with information on blood lipids or glucose, and their relatively higher discrimination may partly reflect this additional metabolic information. The researchers therefore caution that these measures should be considered complementary risk markers rather than standalone tools for predicting or diagnosing disease.
Overall, the study highlights that obesity-related health risks cannot be fully captured by BMI alone. Different measures capture different aspects of body fat distribution and metabolic health, and their associations and discriminatory ability vary across diseases. The findings support a more disease-specific and population-specific approach to obesity assessment and weight management, rather than relying on a single measure for all individuals and health outcomes.
The ChinaHEART project was approved by the central ethics committee of Fuwai Hospital, and all participants provided written informed consent. The study was supported by the National High Level Hospital Clinical Research Funding. The funder had no role in study design, data collection, analysis, interpretation, or the decision to submit the work for publication.
Science Bulletin