A health watchdog is urgent millions of people for the first time to ensure their waist size is less than half their height in order to help stave off serious health problems.
The UK has one of the worst obesity rates in Europe, with two in three adults officially overweight or obese in an escalating crisis that now costs the NHS £6bn a year and wider society £27bn.
The most widely used method to check if a person is a healthy weight is body mass index (BMI), which for most people can accurately measure whether they are a healthy weight for their height. A BMI of 18 to 25 is considered a healthy weight, 25 to 30 is overweight, and over 30 is obese.
But amid increasing concerns over the toll of obesity on the health of the population in England and Wales, for the first time ever, the National Institute for Health and Care Excellence (Nice) will say on Friday that adults with a BMI under 35 should also measure their waist-to-height ratio to stay healthy.
By using the ratio together with BMI, people can work out whether they are carrying excess fat around their middle, which is known to raise the risk of serious conditions, including type 2 diabetes, high blood pressure and heart disease.
Anyone wanting to find out their waist-to-height ratio can use an online calculator, or could ask a health professional to work it out for them. To measure their waist, they should find the bottom of their ribs and the top of their hips, wrap a tape measure around the waist midway between these points and breathe out naturally before taking the measurement.
As an example, a 163cm (5ft 4in) female with a waist circumference of 74cm (29in) would have a healthy ratio, but 81cm would push her into the unhealthy range. A man who is 178cm (5ft 10in) would be at increased health risks if he had a 91cm (36in) waist.
The guideline says a healthy waist to height ratio is 0.4 to 0.49, indicating no increased health risks. A ratio of 0.5 to 0.59 puts people at increased risk of health issues, while 0.6 or more puts them at the highest risk of health problems.
Dr Paul Chrisp, the director of the center for guidelines at Nice, said: “Our updated draft guideline offers people a simple and effective way of measuring their weight so they can understand the factors that could impact on their health and take action to address them .
“Our committee found that a clear benefit of using the waist-to-height ratio is that people can easily measure it themselves, interpret the results, and seek medical advice if they are at increased health risk.”
The guidance also sets out ways to assess childhood obesity and says tailored plans should be considered for children with a high BMI or a waist-to-height ratio above 0.5.
The guideline committee member Prof Rachel Batterham, a consultant in obesity, diabetes and endocrinology, said: “Increased fat in the abdomen increases a person’s risk of developing several life-limiting diseases including type 2 diabetes and heart disease.
“Waist-to-height ratio is a simple, easy-to-use measure that identifies people who are at increased health risk and would benefit from weight management support to improve their health.”