It is no secret that obesity is a major risk factor for cardiovascular disease. But there is some debate around the best way to measure obesity for predicting this risk. Many researchers and health professionals use body mass index (BMI), which is a measure of weight in relation to height. But recent research suggests that waist-to-hip ratio may be a better measure. People with higher waist-to-hip ratios (indicating the presence of more abdominal fat) tend to be at higher risk of cardiovascular disease than people who carry more weight around their hips.

A new study in the November 5, 2005 issue of the Lancet compared the relationship between BMI and waist-to-hip ratio and the risk for heart attack in over 27,000 people in 52 countries. The researchers concluded that waist-to-hip ratio was the best predictor of heart attack risk.

About the Study

This study included 27,098 participants in Asia, Europe, the middle east, Africa, Australia, North America, and South America. About half of the participants (the “cases”) had experienced a heart attack, and the other half (the “controls”) were matched to the cases according to similar age and sex. Researchers measured each participant’s weight, height, and waist and hip circumferences.

After controlling for waist-to-hip ratio and other factors that affect heart attack risk (e.g., smoking, high blood pressure , diabetes, diet, activity, alcohol use), there was no significant relationship between BMI and heart attack risk. By contrast, after controlling for BMI and the other risk factors, waist-to hip ratio was a significant predictor of heart attack. The participants with the highest waist-to-hip ratios were 75% more likely to have a heart attack than those with the lowest ratios. These results held true for men and women and across ethnic groups.

How Does This Affect You?

Currently, many health professionals and researchers use BMI to assess cardiovascular risk, but these findings suggest that waist-to-hip ratio is a more accurate measure for assessing heart attack risk. The researchers estimate that by using BMI instead of waist-to-hip ratio, the risk of heart attack is underestimated by approximately three-fold. While some people may fall into the “ideal” BMI range, their waist-to-hip ratios may indicate that they are at increased risk for heart disease.

To reduce your waist-to-hip ratio, it is important to both decrease abdominal fat by losing weight and to maintain muscle mass through strengthening exercises. People who have more muscle mass tend to have larger hip circumferences, and thus lower waist-to-hip ratios.