How to tell if you are obese

Body Mass Index (BMI)

There are a number of ways in which to assess your weight, however to determine whether you are overweight, the Body Mass Index (BMI) has become the medical standard used by professionals.

BMI is a measure of body fat based on height and weight and is calculated by taking your weight in kilogrammes divided by your height in metres squared.

Find out your BMI

BMI= weight (kg) divided by height² (m²)

You can use the BMI calculator to the left, or follow these steps:

• Find out your weight in kilograms (multiply your weight in stones X 14, and divide the result by 2.2)
• Find out your height in metres (one foot = 30 cm, one inch = 2.45 cm)
• Divide your weight (in kilograms) by your height (in metres)
• Then divide your answer by your height in metres again

BMI is categorised in the following ways:

• BMI less than 18.4 - UNDERWEIGHT
  You may need to gain weight
• BMI of 18.5-24.9 - HEALTHY WEIGHT
  You should aim to stay this way
• BMI of 25-29.9 - OVERWEIGHT
  Good idea to lose weight or prevent further weight gain
• BMI of 30-34.9 OBESE
  Your health is at risk. Losing weight will improve your health
• BMI of 36-39.9 - SEVERELY OBESE
  Your health is at increased risk
• BMI of 40 or more - MORBIDLY OBESE
  Your health is at significant risk

Although morbid obesity is defined as a BMI of 40 or more, people with a BMI of 35 who have a health related condition such as diabetes are also considered morbidly obese.

Note: BMI is not always a good reflection of body fatness. A very muscular person might have a high BMI when in fact their body fat is at a healthy level as muscle weighs more than fat. BMI should be used as a guideline only. Speak to a consultant for further information.

Waist measurement

Excess weight, as measured by BMI, is not the only risk to your health. The location of stored fat can also indicate a risk to your health. Carrying fat mainly round your waist suggests that you are more likely to develop health problems than if you carry the weight on your hips and thighs.

A simple way to establish whether you have too much fat around your middle is to take your waist measurement.

To take an accurate waist measurement:

• Stand with your feet together and your arms at your side
• Relax your abdomen - don't hold your stomach in
• Place a flexible (cloth or plastic) tape measure around your bare abdomen
• Be sure the tape is snug on your skin, but not so tight that the skin pinches together

Women with a waist measurement of more than 35 inches, or men with a waist measurement of more than 40 inches may have a higher disease risk than people with smaller waist measurements because of where their fat lies.