I've written about it for Spectator Health...
As any fool knows, height is measured in double-decker buses and land is measured in football pitches. If you are measuring a very large stretch of land it should be compared to Wales, or possibly Belgium, but there is no need to be more precise than that. It is a robust system of measurement has served Britain well for years, but how should we measure volumes of fluid?
If it is a large body of liquid, an Olympic-sized swimming pool is the proper unit. For smaller quantities, you should use the bath. Most people have a bath tub, and everybody knows it can hold a hold a lot of liquid, so if you want to describe a reasonably large quantity of fluid there is no need to mess around with fancy-pants jargon involving 'pints' and 'litres', you can just say 'enough to fill a bath'.
That was the approach of Cancer Research UK (CRUK) today when they informed us that 'Teenagers drink a bathtub of sugary drinks a year'. In a press release that the BBC grandly described as a 'study', CRUK took data from the National Diet and Nutrition Survey and estimated how many sugary drinks are consumed by 11 to 18 year olds. The answer, they say, is just under two-thirds of a can per day. That doesn't sound like a great deal - and it is significantly less than they were drinking five years ago - but it is more impressive when you multiple it by 365 and put it in a bath. So that's what they did