Waist circumference and BMI

Waist circumference

Waist circumference is a measure of abdominal fat. Having fat around your abdomen ("apple" shape), regardless of your body size, has been linked to an increased risk of diseases such as heart disease and type 2 diabetes. Fat predominantly deposited around the hips and buttocks ("pear" shape) doesn't appear to carry the same risk.

The numbers:

• Aim for: A waist circumference of less than 100cm (men) or 90cm (women).
  
  
• Check it: As often as you like - all you need is a tape measure. Measure your waist at its narrowest point while standing up with your stomach relaxed.
  
  

Body mass index (BMI)

Body mass index (BMI) is a measure of your weight adjusted for height. It gives an approximate measure of your total body fat and indicates whether you're overweight or obese. If you are, you're at risk of developing other conditions such as diabetes, heart disease, high blood pressure, osteoarthritis and some cancers.

The numbers:

• Aim for: 18.5 to 24.9. Less than 18.5 is underweight, 25 to 30 is overweight, higher than 30 is considered obese.
  
  
• Check it: Divide your weight (in kilograms) by your height (in metres) squared. A person who weighs 60kg and is 1.65m tall, for example, has a BMI of 22 (60 divided by [1.65 x 1.65]). This is in the normal range.

Some cautions: The BMI does not distinguish between weight associated with fat and weight associated with muscle so it has its limitations.

• It may over-estimate body fat in pregnant women, athletes and others who have a muscular build. Conversely, it may under-estimate body fat in the elderly and others who have lost muscle mass.
  
  
• It can be misleading in children as body fat changes as they grow. Boys and girls also differ in their body fat as they grow.