Body mass index (BMI) may not tell the whole story about a person’s cardiovascular risk. A large study suggests that measuring where body fat is carried—particularly around the waist—can reveal important differences in risk that BMI alone may miss
The findings, published in the Journal of the American College of Cardiology (JACC), show that people with the same BMI can have substantially different cardiovascular risks depending on how much fat they carry around the abdomen. Some people considered normal weight or overweight by BMI had excess abdominal fat and higher cardiovascular risk. At the other end of the spectrum, some people classified as having obesity had less abdominal fat and lower risk than their BMI might suggest
BMI, calculated from a person’s weight and height, remains widely used to diagnose obesity. But it does not distinguish between fat and muscle or indicate where fat is stored. That distinction matters because visceral fat—the fat surrounding internal organs—is more metabolically active than fat stored beneath the skin. It can promote inflammation, insulin resistance, abnormal lipid metabolism, and other processes involved in cardiovascular and metabolic disease
“Relying on BMI alone, without accounting for measures of central adiposity, can obscure meaningful heterogeneity in CVD risk,” the authors wrote
To investigate whether measures of central adiposity could improve risk assessment, researchers analyzed data from 15 prospective cohorts in the Cross-Cohort Collaboration. The study included 259,351 participants with waist circumference (WC) data and 218,984 with waist-to-hip ratio (WHR) measurements. Median follow-up was 20 years
Among people with a normal BMI, five percent had a high WC and 18% had a high WHR. The mismatch was even more common among those classified as overweight: approximately 40% had elevated central adiposity. That hidden abdominal fat carried consequences. Among normal-weight and overweight participants, a high WC or WHR was associated with a 15% to 50% greater risk of most cardiovascular outcomes, including heart attack, stroke, heart failure, and atrial fibrillation
BMI also appeared to overstate risk for some people. Among participants with obesity, 9% had a low WC and 45% had a low WHR. Those with obesity but a low WC generally did not have significantly greater cardiovascular risk than normal-weight participants with a low WC. Results for WHR were more complex, particularly among women
The population-level findings further underscored the importance of abdominal fat. Among people with obesity, elevated WC accounted for an estimated 49% of heart failure events, 46% of atrial fibrillation events, and 36% of coronary heart disease deaths
The findings add support to recommendations that clinicians look beyond BMI when assessing obesity and cardiovascular health
“Our findings emphasize the critical role of identifying elevated central adiposity, even in individuals with a normal BMI or with a BMI in the overweight range,” the authors concluded. “We encourage clinicians to consider central adiposity distribution across the entire BMI spectrum when evaluating cardiovascular risk in primary prevention settings.”
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