The amount of fat stored around a person's middle may be a more accurate predictor of heart attack risk than body mass index (BMI), a study published in the Journal of the American College of Cardiology (JACC) suggests. Researchers found that waist circumference and waist-to-hip ratio measurements could identify individuals at a substantially higher risk of serious cardiovascular issues, including stroke and heart failure.
Body mass index, a common metric for assessing weight relative to height, has long been used to categorize individuals as underweight, healthy weight, overweight, or obese. However, experts have increasingly pointed out its limitations, as it does not account for body fat distribution, particularly visceral fat, which surrounds vital organs in the abdomen and is known to contribute to organ damage.
The study, which examined the health records of 260,000 participants over two decades, revealed that a significant proportion of individuals classified as having a healthy BMI were found to have high central adiposity, defined as excess fat in the lower middle section of the body. Specifically, 18% of those with a healthy BMI had a worryingly high waist-to-hip ratio, and 5% had a risky waist circumference.
This accumulation of visceral fat can interfere with the function of organs like the liver and pancreas, potentially triggering life-threatening complications. The research indicates that individuals with high waist or waist-to-hip ratios faced a 15 to 50 percent greater risk of experiencing nine major health outcomes studied. These included heart attack, stroke, heart failure, atrial fibrillation, coronary heart disease, cardiovascular disease, and overall mortality.
"We saw individuals with clinically determined normal weight who had elevated central adiposity and high [waist-to-hip ratio], associating them with higher risk across most outcomes," said Michael J. Blaha, senior author of the study. The findings suggest that relying solely on BMI could lead to misclassification of cardiovascular risk.
Zeina Dardari, lead author of the study from Johns Hopkins Ciccarone Centre for the Prevention of Cardiovascular Disease, encouraged clinicians to consider central adiposity distribution across the entire BMI spectrum when evaluating cardiovascular risk. Harlan M Krumholz, editor-in-chief of JACC, added that it is time to move beyond a sole focus on BMI, stating, "Where fat is distributed matters, and these simple measures should be part of routine cardiovascular risk assessment."
Experts recommend measuring waist-to-hip ratio as a simple and reliable method for calculating this risk. The process involves measuring the waist at its narrowest point and the hips at their widest point, then dividing the waist measurement by the hip measurement. According to government guidance, a healthy waist circumference is less than half of a person's height. The World Health Organization suggests a waist-to-hip ratio above 0.9 is dangerous for men and 0.85 for women.
The study's limitations include the absence of data on physical activity, diet, and genetic obesity risk factors, all of which are associated with cardiovascular disease. Additionally, waist measurements were taken only once, preventing an assessment of how changes in fat distribution over time might affect heart health.