Measuring the ratio of someones waist to their height is a better way of predicting their life expectancy than body mass index BMI, the method widely used by doctors when judging overall health and risk of disease, researchers said.
BMI is calculated as a persons weight in kilograms divided by the square of their height in metres, but a study found that the simpler measurement of waistline against height produced a more accurate prediction of lifespan.
People with the highest waist-to-height ratio, whose waistlines measured 80 per cent of their height, lived 17 years fewer than average.
Keeping your waist circumference to less than half of your height can help prevent the onset of conditions like stroke, heart disease and diabetes and add years to life, researchers said.
For a 6ft man, this would mean having a waistline smaller than 36in, while a 5ft 4in woman should have a waist size no larger than 32in.
Children in particular could be screened as early as five using the waist-to-height ratio to identify those at greatest risk of obesity and serious health conditions later in life, it was claimed.
Researchers from Oxford Brookes University examined data on patients whose BMI and waist to height ratio were measured in the 1980s.