We all worry about our weight sometimes - in such an image-obsessed society it’s only natural that we sometimes look in the mirror and think: “Should I maybe hit the gym?”

Most of the time, unfortunately, the answer is yes. Keeping the weight of the UK population down has been a concern for the country’s medical professions for decades now, as the average western diet has ballooned in calories.

The answer, seemingly, is to measure everyone using the Body Mass Index (BMI) - which is calculated by dividing your weight (in kilograms) by your squared height (in metres). This is generally a good indication of ideal weight, which is in itself a good indication of health, but there are deep flaws in the methodology - and should it really be used for children?

The biggest mistake, and one that people often point to, is muscle mass. Muscle weighs twice as much as fat, and therefore athletic people can score very highly on the BMI scale despite having very little body fat.

James Haskell, the former England rugby union player and recent I’m A Celebrity contestant, is considered obese by the BMI scale, despite having a six pack.

That said - most of us are not international rugby players and sticking to BMI ensures that we reduce our risk of weight-related problems.