It is a long-held belief that body mass index (BMI) is the best way to classify obesity and therefore predict the degree of cardiovascular risk associated with excess body weight.

Recently, more attention has been focused on waist to hip ratio (WHR), in particular as a marker of central obesity and insulin resistance. It is therefore not unreasonable to consider that WHR may be a better way to assess obesity, at least from a cardiovascular point of view.

A study has quantified the association between different measures of obesity and the prevalence of atherosclerosis and found WHR to be the best marker.

A population-based cohort study using data from the Dallas Heart Study assessed three measures of obesity in nearly 3,000 patients: BMI; waist circumference and WHR. The degree of atheroma present was assessed in 2,744 patients, using electron-beam computed tomography to calculate a coronary calcium score (an accepted surrogate for coronary atheroma). The study looked for aortic plaque using MRI in 2,504 patients.

After adjustment for standard risk factors, the results showed that significantly more coronary calcium was found in patients in the highest quintile of WHR compared with the lowest quintile (OR 1.91, 95% CI, 1.30-2.80). No such association was observed with BMI or waist circumference. Similar results were found for aortic plaque.

Therefore it would appear that waist to hip ratio is the better marker for predicting underlying coronary and aortic atheroma. Perhaps we should be focusing more on this than the more traditional BMI for quantifying obesity in our patients.