DR MICHAEL MOSLEY: Can you pass the string test? A brilliantly simple way to check your fat

To start the string test you need to cut a piece of string which is as around as tall as you are A warning that being overweight is bad for you is hardly news, but the message was hammered home last week by yet another big study, based on data collected from more than 2.8 million British patients. And for this reason, you can be fairly light, with a low BMI, and yet have far too much body fat, particularly gut fat. If you struggle to do this, it suggests that you are carrying too much weight around your middle, and therefore, your visceral fat level is probably too high. He is worried that it misses lots of what he calls normal-weight obesity: people who have a low BMI but relatively little muscle and a high percentage of body fat. ‘Compared to fat around the hips, fat around the waist is more metabolically active, is closely related to insulin resistance and seems to be more strongly associated with the risk of heart disease, stroke and diabetes.’ The build-up of visceral fat is normally the result of a number of different factors, which include eating too much sugary, starchy food, drinking too much alcohol, not doing enough exercise, feeling stressed and sleeping badly, and, of course, genetics.