How to work out your BMI to determine obesity

Obesity has reached epidemic proportions in the UK and worldwide, with one in five people in England now classed as obese.

Being obese not only makes life difficult by reducing your mobility and quality of life, it also significantly increases your risk of developing long-term conditions such as cardiovascular disease and diabetes.

But with the average woman’s dress size increasing decade on decade, it is easy to fall into the trap of thinking that being ‘average’ means you are not overweight.

The best way to assess whether you need to lose weight – and the method used by healthcare professionals – is to look at your body mass index, or BMI. This uses a formula that combines your weight and height to give you a final number, which you can then check against standardised categories to see which one you fall into.

The formula for working out your BMI is:

Weight in kilograms / (height in meters x height in meters)

So you need to work out your height in meters and multiply it by itself to give your height squared. Then take your weight in kilograms, and divide that by the answer you got for you height squared.

When you have the answer, see which of these categories you fall into:

* BMI below 18.5 = underweight

* BMI between 18.5–24.9 = healthy range

* BMI of 25–29.9 = overweight

* BMI of 30–34.9 = obese

* BMI of 35–39.9 = severely obese

* BMI of 40–49.9 = morbidly obese

* BMI of 50 or more = super obesity

Morbid obesity means obesity that poses a very high risk to health, although even just being classified as overweight also poses a moderate health risk.

Another way to assess risks associated with your weight is by measuring your waist circumference: for men, risks increase with a waist measurement of over 40 inches (102 cm), while in women, the risks are increased when waist circumference is greater than 35 inches (88 cm).

So don’t be in denial – know your numbers so you can take steps to minimise your risk of long-term complications.