The body mass index (BMI), or Quetelet index, is a measure of relative weight based on an individual’s mass and height. It is defined as the individual’s body mass divided by the square of their height – with the value universally being given in units of kg/m2. It is used as a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults.
The BMI is used in a wide variety of contexts as a simple method to assess how much an individual’s body weight departs from what is normal or desirable for a person of his or her height. There is, however, often vigorous debate, particularly regarding at which value of the BMI scale the threshold for overweight and obese should be set, but also about a range of perceived limitations and problems with the BMI.
What is a healthy BMI?
For most adults, an ideal BMI is in the 18.5-24.9 range.
If your BMI is 25 or more, you weigh more than is ideal for your height.
25-29.9 is overweight
30-39.9 is obese
40 or more is very obese
If your BMI is less than 18.5, you weigh less than is ideal for your height.
If your BMI is 25 or more, you should think about losing weight. Being overweight or obese can increase your risk of health problems, such as:
Type 2 Diabetes
Some types of Cancer
High blood pressure (Hypertension)
Healthcare professionals use the words ‘obese’ and ‘obesity’ as clinical terms to describe your increased risk of health problems. They do not use these terms to describe what you look like.
If your BMI is less than 18.5, you may want to talk to your doctor about gaining weight. Being underweight can also increase your risk of health problems, such as:
Brittle bones (Osteoporosis)
Absent periods in women (Amenorrhoea)
Iron deficiency Anaemia
Accuracy of BMI
As well as measuring your BMI, healthcare professionals may take other factors into account when assessing if you’re a healthy weight.
Muscle weighs more than fat. Very muscular people, such as heavyweight boxers, weight trainers and athletes, may be a healthy weight even though their BMI is classed as obese.
Your ethnic group can also affect your risk of some health conditions. For example, adults of Asian origin may have a higher risk of health problems at BMI levels below 25.
You should not use BMI as a measure if you’re pregnant.
You can calculate your BMI easily by clicking on the link here.