ONTARIO—The best way to check heart attack risk in the obese isn’t body mass index (BMI); a person’s waist-to-hip ratio was far more effective, according to new, global research.

In a study published in The Lancet medical journal, researchers assessed whether other markers for obesity, especially waist-to-hip ratio, would be a stronger predictor of heart attack than the conventional measure of BMI in different ethnic populations. Previous research has shown that obesity increases the risk of heart disease; however, most have been done in European and North American populations.

The investigators looked at BMI, waist-to-hip ratio, waist measure, and hip measure in more than 27,000 people from 52 countries. Half the participants had previously had a heart attack and half were age and sex-matched controls (individuals who had not had a heart attack and were the same age and sex as cases). The team found that BMI was only slightly higher in heart attack patients than in controls, with no difference in the Middle East and South Asia. By contrast, heart attack patients had a strikingly higher waist-to-hip ratio than controls, irrespective of other cardiovascular risk factors. The researchers found that this observation was consistent in men and women, across all ages, and in all regions of the world.

The authors' found that compared with BMI, waist-to-hip ratio is three times stronger than BMI in predicting the risk of a heart attack. Larger waist size (which reflects the amount of abdominal fat) was harmful, whereas larger hip size (which may indicate the amount of lower body muscle) was protective.

"Our findings suggest that substantial reassessment is needed of the importance of obesity for cardiovascular disease in most regions of the world," said Salim Yusuf, director of the Population Health Research Institute at McMaster University and Hamilton Health Sciences. The waist-to-hip ratio is calculated by dividing the waist measure by the hip measure. The cut off point for cardiovascular risk factors is less than 0.85 for women and 0.90 for men. A higher number denotes more risk.

The study was funded by the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario and 37 other funding sources, including unrestricted support from several pharmaceutical companies.