A flaw in the scale?

The Seventeen BMI calculator taken as a screenshot by recovering anorexic Shirley Wang before the  removal of the feature from the website.

Last November, a petition was sent to the teen magazine Seventeen with over 2,700 signatures requesting the removal of the hideously flawed BMI calulator from their website. The site proclaimed a BMI of 15 to be within the healthy range for an 18 year old girl - for sense of scale, that would mean a 5'6" young lady weighing in at less than 95 pounds.

The calculator has been removed, thankfully, but the problems brought up by the feature have highlighted a lot of problems in the scale we use for defining our physiques. Putting aside the fact that the "healthy BMI range" given here appears to be be pulled out of someones nether-regions, is BMI of any use to any one whatsoever?

The original BMI measurement system has been around for 150 years and is used nowadays to sort people into categories from underweight to morbidly obese dependent on the calculation: 

• weight (in kilos)/(height (in meters) squared)

This system is renowned for being wildly inaccurate, as it fails to take into account any sort of variations in gender or athletic build. Physicians will take into account factors such as age, blood pressure and body fat percentage when accessing someone's health, yet the average person at home on the sofa will simply enter their height and weight into any one of hundreds of online calculators.

Using this calculation, short people are frequently calculated as being "thinner" than they are, whilst tall people come out as "fatter". Large-breasted women often come out several point higher than they actually would be with "average" sized breasts, even if there is not an inch of fat on the rest of their bodies.

A more accurate calculator has recently be devised by Nick Trefethen, a Professor of Numerical Analysis at Oxford University:

• 1.3 x weight / height to the power of 2.5

Whilst this is all very reassuring to those at either end of the scale, the greatest flaws with BMI are at a societal level.

As a girl, I remember weighing myself and calculating my BMI on almost a weekly basis. I wanted to compare myself to my friends who were all much taller and thinner (and generally more glamorous and elegant) than I, I wanted my BMI to match theirs, thinking it would make me just a smaller version of them. I still now feel the need to calculate my BMI every time I weigh myself, aiming for that all elusive number.

The impact that this can have on any one person (young or old, male or female) is immense. In all likelihood  the result of trying 50 different ridiculous diets in early adulthood is just going to be the gain of an extra stone or three in the following years.

So why do we still use BMI? Probably because it is neat and simple. It allows us to put ourselves into boxes of "healthy" vs "unhealthy".

Yet the human body is a hugely complicated bit of machinery and every single one of them is different. Any approach to categorizing them is going to be flawed from the start.

Instead, there are other measurements and factors that one can use to judge their health if they so wish. These are much more subjective, they don't involve any neat equations and they require us to actually trust and understand our bodies.

It really revolves around how healthy you feel. Things like generally clear skin, strong teeth and thick hair tend to be noticed by the opposite (or same) sex very quickly when it come to finding prospective partners as they are good (if general) indicators of a healthy human being.

For women, a hip to waist ration of around 0.65-0.85 (a massive range, covering many body types) is well within the healthy body structure - a recent study has seen that men see a ratio of 0.7 as ideal as this is a sign of high fertility...

As for your general health, if you can comfortably walk a mile in 15-20 minutes without getting out of breath, if you can make it up three flights of stairs without needing a time out, if you eat a few green things (vegetable green, not gummy sweet green) a day, you are probably alright.

Small changes in lifestyle can have big changes in your health, trite but true. Take the stairs, not the lift; walk, don't take the bus; put down the takeaway and cook a proper meal. These will help out your body, and also your bank balance.

Every body is different, every body as an "ideal weight" that it will gravitate towards. The most important thing to remember is that no one knows your body like you. If you think you need to change in either direction, larger or smaller, DO see a doctor first. They will give you good advice and help you to feel the way you should feel.