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Measuring overweight and obesity


There are two key ways in which we presently determine whether people are overweight or obesity these are

  • Body Mass Index (BMI),

  • Waist measurements.

Body Mass Index (BMI)


The most widely recognised definition of obesity is in terms of BMI. The higher the BMI the greater the risk of morbidity and mortality. To calculate a BMI you need to times your height in metres by itself then divide your weight by the height squared.


For example: if you are 1.6m tall and weigh 65kg the calculation would be 1.6 x 1.6 = 2.56. BMI would be 65 divided by 2.56 = 25.39


BMI Categories:

  • Underweight   below 18.5

  • Normal weight    18.5-24.9

  • Overweight 25-29.9

  • Obese 30 – 40

  • Morbidly obese 40 or above

Waist Measurements


The current World Health Organisation guidelines are that your health is at risk if you waist measurement is:-


Men Over 94 cm (about 37”)

Women Over 80cm (about 31”)


British Obesity Society think it might be easier if you follow the simple guidelines of Dr Margaret Ashwell which is;


Measure your height, and your waist measurement should be no more than half your height. For example if you are 6’ (72”), your waist should be 36” or less. It does not matter if you measure in inches or centimetres the same principle applies.


How to measure your waist

  1. Find the top of your hip bone and the bottom of your ribs.

  2. Breathe out normally.

  3. Place the tape measure midway between these points and wrap it around your waist.

  4. Check your measurement.

The NHS have created a useful weight calculator - click here to be redirected to it.



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