Waist-to-height ratio (WHtR)

The waist-to-height ratio (WHtR) is one of the simplest and most meaningful indicators of your health risk: waist circumference divided by height. The rule of thumb from British nutrition scientist Margaret Ashwell is: keep your waist to less than half your height. So if you're 170 cm tall, your waist should measure less than 85 cm.

Values from 0.4 to 0.49 are considered unremarkable, 0.5 to 0.59 indicate increased risk and 0.6 or more significantly increased risk; a value below 0.4 can point to underweight. Unlike BMI, the WHtR captures where fat is stored – and belly fat is the key factor for type 2 diabetes, high blood pressure and heart disease. Studies show that the WHtR predicts these risks better than BMI alone; since 2022, the UK's National Institute for Health and Care Excellence (NICE) has explicitly recommended it alongside BMI.

How to measure correctly: in the morning, before eating, with nothing on around your middle. Place the tape measure horizontally midway between your lowest rib and your iliac crest (the top edge of your hip bone) – for most people, roughly at the level of the belly button. Breathe out normally – don't pull your stomach in or push it out – then read the measurement. Measure twice and take the average.

The big advantage of the WHtR: it works largely independently of sex, age and build – and the 0.5 rule already applies to children from around the age of five, because waist and height increase together during growth. For children, the paediatrician with their percentile charts is still the first port of call. For older people, some experts suggest slightly more generous limits – if in doubt, your GP will interpret the value together with your blood pressure and blood test results.

And if the value is too high? Belly fat responds pleasingly quickly to more exercise, less alcohol and sugar, and better sleep – your waist measurement often drops before the scales show anything.