Interactive calculator: do you win or lose with the new BMI?

[Jazzy]

The body mass index has been around since Belgian scientist Adolphe Quetelet invented it in the 1830s and was designed to approximate whether people have a healthy weight.



By dividing a person's weight in kilograms by their height in metres it is possible to arrive at an estimate of that individual's body fat.



Nick Trefethen of Oxford University's Mathematical Institute has identified a flaw in the basic formula for BMI, and has created a new calculation which he says better accounts for the relationship between height and weight.



According to Mr Trefethen, the current formula to calculate the score (weight/height2) is incorrect because it divides the weight by too large a number for short people, and too small a number for tall people. So short people are misled into thinking they are thinner than they are, and tall people are misled into thinking they are fatter than they are.



His new formula (1.3 x weight/height2.5) is a better approximation of reality, because it scales more accurately as a person grows in height.



The result of the change is that shorter people under five feet might gain a BMI point, while taller individuals over six foot could lose one.



Dr Trefethen suggests that the reason the old formula has lasted so long is because when Quetelet invented the BMI, there were no calculators or computers so it was better to have a formula that was easy to calculate, than a complex one that no-one would use.

Click here to try the interactive calculator



Well, according to the calculator, I'm considered underweight.



In what range did you score?

 

[Evil Eye]

Underweight. I dropped .8 points.

Meh.

 

[Jazzy]

@EE: I don't consider myself underweight. Do you consider yourself underweight?

 

[Evil Eye]

Hmm, there's no weight to lose, but it's not like I'm malnourished.

Can't say I ever really think about it.

 

[Geoffrey]

Old system I'm 18.8 and on the new system I'm 17.6. Underweight, but also still in the borderline area (just had this section in my health class) so it's not really a problem.