Waist size flags heart disease risk better than BMI in large study

WASHINGTON - Fat around the midsection predicts future heart disease better than body mass index alone, according to a large study published in JACC, the flagship journal of the American College of Cardiology.

Researchers in the Cross Cohort Collaboration followed more than 260,000 people for an average of about 20 years. Participants had waist circumference or waist-to-hip ratio data and were tracked for nine outcomes, including heart attack, stroke, heart failure, atrial fibrillation, and death from heart disease or any cause.

BMI is weight in kilograms divided by height in meters squared. It is widely used to label overweight or obesity, but it does not show where fat sits. Visceral fat around the organs is more strongly tied to heart disease and diabetes than fat just under the skin.

Among people with a normal BMI, about 5 percent had a high waist circumference and 18 percent had a high waist-to-hip ratio. Among those overweight, about 39 percent had high waist circumference and 40 percent had high waist-to-hip ratio. People with normal weight or overweight who still had high central fat measures faced 15 percent to 50 percent greater risk for most of the nine outcomes studied.

Senior author Dr. Michael J. Blaha of the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease said waist and waist-to-hip measures reclassify risk that BMI alone can miss. Lead author Zeina A. Dardari said relying only on BMI can misclassify cardiovascular risk across a wide range of outcomes.

JACC editor-in-chief Dr. Harlan M. Krumholz said the study, based on hundreds of thousands of participants, shows that where fat is distributed matters and that simple waist measures should be part of routine risk assessment.

The study did not include detailed physical activity, diet, or genetic obesity risk, and it used a single waist measurement rather than changes over time. Authors still urged clinicians to consider central fat across the full BMI spectrum in primary prevention.