Researchers and clinicians have long debated whether body mass index provides a reliable picture of a person's weight-related health status. Its calculation draws on only two figures — body weight and standing height — leaving out how fat is distributed across the body, the proportion of lean muscle, and additional physiological variables that researchers have linked to health outcomes.

Decades of accumulated research momentum, along with the near-two-century lifespan of BMI as a standard tool, have kept any alternative from taking hold.

Researchers whose findings landed in Science Bulletin set out to determine whether alternative obesity measurements carry stronger predictive value for assessing health risks than existing indices. Drawing on health records covering more than four million adults aged 35 to 75 from the ChinaHEART cohort, a group of medical researchers investigated the question. Fifteen obesity-related indices, drawn from three distinct measurement categories — body shape, visceral fat distribution, and metabolic function — were put through a comparative analysis to determine how each connected to the onset of chronic disease.

Elevated readings across most of the measured indices pointed toward greater likelihood of cardiovascular disease and diabetes, whereas associations with chronic obstructive pulmonary disease and cancer were considerably less pronounced. Certain measures produced non-straightforward relationships with those conditions, including patterns that ran counter to the expected direction. The data indicate that no single measurement tool appears capable of accounting for the full spectrum of health complications tied to excess body weight.

Across all the indices examined, the researchers tested how effectively each measure could separate people according to their varying exposure to chronic disease risk, and the results pointed to wide differences in performance. Cardiovascular disease risk was better captured by the Chinese visceral adiposity index, whereas the triglyceride-glucose index proved more reliable for gauging diabetes risk.

Of all the measures examined, a body shape index — which captures the ratio of abdominal fat relative to overall body size and has traditionally been applied to gauge the likelihood of early death, heart disease, and diabetes — returned the strongest association with chronic obstructive pulmonary disease risk. The researchers noted that where fat accumulates in the body plays a role in how well the lungs and airways operate.

Among all the obesity-related measures examined, not one returned a meaningful link to cancer, placing it apart from the other conditions in the analysis. Associations identified across other conditions were limited in strength.

The study team acknowledged that, with participants drawn entirely from mainland China, the findings may have limited transferability to populations of different ethnic backgrounds.