Years ago people used to weigh themselves to find out if they were overweight. There were height and weight tables you could look up to see whether your weight was low, normal or high for your height. It was all so simple back then.
But doctors argued it wasn't an accurate enough way to determine whether or not you were really overweight. And so body mass index (BMI) became the official measurement of how fat you were. But apparently even BMI isn't good enough any more, and a new measurement is set to take over, called body adiposity index (BAI).
Writing in the journal Obesity, researchers from the University of Southern California claim BAI is more flexible than BMI - and therefore more accurate. BMI, they claim, is too general, as it's a calculation that uses your weight and height and not how much muscle or body fat you have.
So, for instance, if you have a lot of muscle - like a rugby player, for instance - you might have the same BMI as someone who has a lot of body fat and classed as overweight or even obese.
BAI, on the other hand, is a more useful measurement of body fat, they say. However it sounds even more complicated than BMI (which is your weight in kilograms divided by your height in metres squared). BAI uses a complex ratio of your hip measurement to your height - but like BMI, you need a computer or a calculator to work it out.
So will BAI catch on? Are the days numbered for BMI? Or should we just go back to the good old bathroom scales?