Body mass index (BMI) is currently used as the most accurate and reliable way of measuring how overweight you are. You can use the healthy weight calculator to calculate your BMI. You will need to know your height and your weight.

For most adults, a healthy weight is having a BMI between 18.5 and 24.9. A BMI between 25 and 29.9 is considered overweight. A BMI over 30 is considered obese.

The BMI calculation cannot take into account very muscular figures. Muscle can add extra weight, and this may give you an overweight or obese BMI, when you are not an unhealthy weight. For example, a heavyweight boxer would be classed as obese using the BMI, when he is in fact a healthy weight.

Though for most people, BMI remains an accurate method of assessing their weight.

Children and young people should not use BMI to calculate if they are a healthy weight, as their bodies are still developing. Instead, children and young people should visit their GP, who will be able to tell them if they are overweight or obese for their height and sex.

Most modern leisure centres have weighing scales that can electronically measure the percentage of your body weight that is fat. This can be compared with what would be ideal for you depending on your height, age and sex. This may give you an indication of how overweight you are.

Visiting your GP

If you are overweight or obese, you should visit your GP to find out if you are at increased risk of health problems, and how you can safely lose weight. Your GP will ask about:

• any underlying causes for your obesity - for example if you are on certain medication or if you have a medical condition that causes weight gain,
• your lifestyle - particularly your diet and how much physical activity you do, and also whether you smoke, and how much alcohol you drink,
• how you feel about being overweight - for example, if you are feeling depressed about it,
• how motivated you are to lose weight, and
• your family history of obesity and other health conditions, such as diabetes (a condition caused by too much glucose in the blood).

Further tests

As well as calculating your BMI, your GP may also perform some further tests. These will help determine if you are at increased risk of any heath complications because of your obesity. These could include:

• measuring your blood pressure,
• measuring your waist circumference (the distance around your waist), and
• measuring the glucose (sugar) and lipid (fat) levels in a sample of your blood.

Your GP may also consider your age and ethnicity, as these can affect your risk of certain conditions. For example, some people of Asian, African or Afro-Caribbean ethnic groups may be at increased risk of high blood pressure (hypertension), and some older people may be at lower risk.