Dating overweight person
A ratio of 1.0 or more in men, or 0.85 or more in women, suggests an apple shape, meaning a raised risk of future health problems.
In a recent study involving nearly 3,000 people aged 16 and older, she found that more than a third of those with a 'normal' BMI would have been classed as at risk by the string method.
Dr Ashwell says the key is to ensure your waist measurement is less than half your height.
The easiest way to check this is to measure your height with a piece of string, then fold that in half and check it fits comfortably round your waist.
This method is more likely to detect the at-risk apple shape and is a more reliable indicator than waist circumference alone, she says, as that fails to take into account height (a bigger waist size may be healthy in a very tall, broad person).
The waist-to-hip ratio is 'not bad at identifying apples and pears', she adds, but 'it doesn't help much when people lose weight, because they'll tend to lose some off their waist and some off their hips, so the ratio won't change'.