What is ‘overweight’ and ‘obesity’?
People are considered as being affected by overweight or obesity when there is an excessive amount of fat stored in the body.
Fat is the main way that the body stores energy. If you consume more energy than your body needs, your body converts it to fat that can be converted back to energy later when it’s needed. Over time, if you continue to take in more energy than you use, fat builds up in your body.
Not all body fat has the same effect on your health. Fat located under the skin (subcutaneous fat) is needed by the body for insulation, protection and normal metabolism function. Fat that accumulates in the abdomen and around your organs can cause serious health problems.
The definitions of overweight and obesity
Body Mass Index (BMI)
People are classified as overweight if they have a body mass index (BMI) of more than 25 kg/m2 (body weight in kilograms/square of height in meters), and obese if their BMI is 30 kg/m2 or more. BMI is not a good measure of how much body fat an individual has.
Waist circumference
A useful way to assess the amount of fat in your abdomen is to measure your waist circumference. This is the distance around the waist, halfway between the top of your hips and the bottom of your ribs (not necessarily at the level of your belly button).
In Caucasian males, a waist circumference of 94cm or more is associated with a higher-than-normal risk of chronic (long-term) diseases like type 2 diabetes, cardiovascular disease and many cancers. A waist circumference of 102cm or more is associated with even greater risk. Males of different ethnicities have different waist circumference thresholds for increased risk of chronic disease.
| Ethnic group | Waist circumference (cm) |
| Chinese | ≥80 |
| Japanese, Tunisian | ≥85 |
| Iranian | ≥89 |
| Korean, Asian Indian | ≥90 |
| Caucasian | ≥94 |
| Jordanian | ≥98 |
How common is overweight and obesity?
In Australia, 18.2% of boys are overweight and an additional 8.6% are obese, and 34% of adult males are overweight and 31.7% are obese.
Overweight and obesity are around twice as common in Aboriginal and Torres Strait Islander boys and young men than in their non-Indigenous counterparts.
Based on waist circumference, 22.9% of Australian adult males are at an increased risk of complications, and 40.6% are at a substantially increased risk.
What are the causes and risk factors for overweight and obesity?
Major factors causing obesity in Australian males are:
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What are the health consequences of overweight and obesity?
Too much fat in the body causes problems with how your body functions, which can result in diseases affecting metabolism and psychological wellbeing.
Overweight and obesity is the leading contributor to poor health in Australian males.
How are overweight and obesity treated?
There are some key things that you can do to lose excess body fat.
Changes in diet and physical activity are part of all treatments for overweight and obesity. Weight loss programs that involve a combination of strategies for changing eating and physical activity, supported by regular contact with someone trained in helping people to lose weight, are an effective way to lose weight.
Medications or surgery for weight loss are effective but they have side effects or risks that make them unsuitable for everyone, and they are only used if changes to eating and physical activity don’t achieve enough weight loss.
Some medications for other health problems can cause you to put on weight. You might need to change the way you eat or do some exercise to avoid this side effect, or there might be an alternative medication you can change to.
Want to learn more about weight loss injections?
Understand what medications like Ozempic are, what they should be used for and whether they're right for you. Read here.
What to do about overweight and obesity
If you think you might be overweight, you should talk to your doctor. They can work out whether there are any adverse health effects and advise about any changes you should make to your eating or activity level. They can also work out if there is something else (e.g. medication, stress, other health problems) that might be contributing to you gaining weight.
Sudden changes to your diet or activity level might be harmful to your health, so it’s best to talk to your doctor before making big changes.
