Waist to height ratio is a better predictor of heart disease and diabetes risk than BMI, according to new research presented at a scientific meeting recently.
Study leader Dr Margaret Ashwell, an independent consultant and former science director of the British Nutrition Foundation, presented the findings at the 19th Congress on Obesity in Lyon, France, on Saturday 12 May.
"Keeping your waist circumference to less than half your height can help increase life expectancy for every person in the world," said Ashwell, as reported in the Telegraph.
Thus a man who is 6ft or 72 inches tall (183 cm), should keep his waist under 36 inches (91 cm), and a woman who is 5ft 4 in or 64 inches tall (163 cm), should keep her waist measurement under 32 inches (81 cm).
Ashwell said the measure should be considered as a screening tool.
The idea of using Waist to Height Ratio (WHtR) to predict cardiometabolic risk is not new, but is coming to prominence as more studies reveal its value.
At the meeting, Ashwell presented the findings of a study that analyzed the health of 300,000 people and found WHtR was better able to predict high blood pressure, diabetes, heart attacksand strokes than BMI.
BMI (short for Body Mass Index) is a widely used measure of obesity. It is a ratio of a person's weight in kilos to the square of their height in metres. However, it does not take into account the distribution of fat around the body.
Abdominal fat affects organs like the heart, liver and kidneys more adversely than fat around the hips and bottom, in terms of cardiometabolic risk.
Last year, Ashwell co-authored a paper on the increasing importance of using Waist-to-Height Ratio (WHtR) to assess cardiometabolic risk, and pleaded for scientists to use a consistent terminology to express the ratio so it can easily be searched for in the literature.
An advantage of WHtR is the simplicity of the health message "keep your waist circumference to less than half your height". This is a much easier thought to hold in mind than BMI, where not only do you have to work out the ratio of your weight in kilos to the square of your height in metres, but also remember what the healthy range is.
To measure the waist circumference accurately, you should measure it mid-way between the lower rib and the iliac crest (the top of the pelvic bone at the hip), this is the method recommended by the World Health Organization, says Ashwell.