Healthdirect Free Australian health advice you can count on.

Medical problem? Call 1800 022 222. If you need urgent medical help, call triple zero immediately

healthdirect Australia is a free service where you can talk to a nurse or doctor who can help you know what to do.

beginning of content

Obesity diagnosis (including BMI)

3-minute read

Body mass index (BMI)

Body mass index (BMI) is often used to assess if you are overweight or not.

How to measure your BMI

To measure your BMI you will need to know your height and waist measurement in centimetres and weight in kilograms. It is easiest to use a BMI calculator to measure your BMI.

For most adults:

  • between 25 and 29, you would be considered overweight
  • between 30 and 39, you would be considered obese
  • 40 or more, you would be considered very 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 male heavyweight boxer would be classed as obese using the BMI, when he is in fact a healthy weight for him.

However, for most people, BMI remains an accurate method of assessing 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 doctor, who will be able to tell them if they are overweight or obese for their height and sex.

Waist circumference

Another useful method to assess your weight is to measure your waist circumference. Men whose waist measurement is 94 cm or more and women whose waist measurement is 80 cm or more are more likely to develop obesity-related health problems, such as type 2 diabetes, heart disease and some types of cancer.

How to measure your waist circumference

It is important to measure your waist circumference accurately.

  1. Place a tape measure directly on your skin, or on no more than one layer of light clothing. Make sure the tape is snug, without squeezing the skin.
  2. Make sure to place the tape measure horizontally halfway between your lowest rib and the top of your hipbone. This is roughly in line with your belly button.
  3. Breathe out normally and take the measure.

Visiting your doctor

If you are overweight or obese, visit your doctor to find if you are at increased risk of health problems, and how you can safely lose weight. Talk to your doctor about:

  • any underlying causes your might have for your obesity - for example, if you are on certain medication or 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
  • your family history of obesity and other health conditions, such as diabetes (a condition where there is too much glucose (sugar) in the blood)

Are you at risk?

Find out if you're at risk of heart disease, type 2 diabetes or kidney disease using our Risk Checker.

Further tests

As well as calculating your BMI, your doctor may also perform tests to determine if you are at increased risk of health complications because of your obesity. These could include:

  • measuring your blood pressure
  • measuring the glucose (sugar) and lipid (fat) levels in your blood

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: July 2018

Back To Top

Recommended links

Need more information?

These trusted information partners have more on this topic.

Top results

LiveLighter - Cardiovascular Disease and the link between overweight and obesity

Overweight and obese are terms used to describe the body weight of people who are carrying excess body fat. To determine whether someone is overweight or obese, their body mass index (BMI) is calculated using their height and weight.

Read more on LiveLighter website

The facts on overweight & obesity in Australia » Dietitians Australia

Medical The facts on overweight & obesity in Australia The facts on overweight & obesity in Australia We all want to be healthy, and we know being overweight or obese is a risk for many health problems in the long run

Read more on Dietitians Association of Australia website

Obesity and overweight -

Energy-dense foods (those that have a lot of kilojoules in a small volume) can be associated with weight gain, especially if you eat a lot of them. These foods tend to be high in sugar and/or fat.

Read more on myDr website

Assessing Central Obesity: Waist Circumference | myVMC

Waist circumference: Measuring waist circumference (WC) is the simplest way to assess central obesity. Central obesity is an excess accumulation of fat in the abdominal area, particularly due to excess visceral fat.

Read more on myVMC – Virtual Medical Centre website

How exercise can help safely tackle obesity

Obesity is a major issue in our society, but exercise must be carefully managed. Find out how here.

Read more on Exercise and Sports Science Australia (ESSA) website

Childhood obesity -

More than one in 4 kids aged 5-17 years in Australia is above a healthy weight. Find out how to help kids make changes to their diet and activity levels.

Read more on myDr website

Weightloss -

People who are overweight or obese are more at risk of health problems. Reducing your weight reduces many of these risks. Find out what products are available for weight loss.

Read more on myDr website

Kids' Health - Topics - What is obesity?

Obesity is what doctors call it when you have too much body fat

Read more on Women's and Children's Health Network website

Childhood obesity in Australia | Raising Children Network

Childhood obesity is when children have too much body fat. Read how a healthy family lifestyle helps kids avoid obesity and benefits health and wellbeing.

Read more on website

Maintain a healthy weight | Cancer Council

By maintaining a healthy body weight, being physically active every day and enjoying a healthy diet, you can lower your cancer risk. Find out how here

Read more on Cancer Council Australia website

Healthdirect 24hr 7 days a week hotline

24 hour health advice you can count on

1800 022 222

Government Accredited with over 140 information partners

We are a government-funded service, providing quality, approved health information and advice

Australian Government, health department logo ACT Government logo New South Wales government, health department logo Northen Territory Government logo Government of South Australia, health department logo Tasmanian government logo Government of Western Australia, health department logo