Reference: Heart 2006; 92:865-6
The most common method of assessing body weight in clinical practice is the body mass index (BMI) which is calculated by taking the weight in kilograms and dividing by the height in metres2. A BMI of 25-29.9 is regarded as overweight, whereas a BMI of 30 kg/m2 or above is classified as obese. This editorial discusses the results of the Interheart study of 15,000 patients which found that the ratio between the waist and the hip measurement predicted the risk of a heart attack more accurately than using BMI alone. The problem with BMI is that because it is simply an expression of the relationship between weight and height, it tells the doctor nothing about where the fat is deposited. This is very important because fat deposited over the waist area (visceral fat) presents a much greater health risk than fat around the hips and thighs. Hence a high waist-hip ratio reflects a large waist measurement relative to the hips and a higher proportion of the risky visceral fat. Even in patients with a BMI as low as 23 a high waist-hip ratio predicted an increased risk of heart attack.
Comment from Dr David Ashton
A number of studies have shown that waist-hip ratio or waist measurement alone are better predictors of risk than BMI. This study again shows that BMI is a poor discriminator of risk at an individual level and should not be used as the sole measure of obesity. It is likely that BMI will become much less important in the assessment of obesity as more discriminating measures are introduced.
