Weight & Health
 min read

Overweight vs obese: The differences explained

The terms overweight and obese are often used together but they mean different things. Our doctors explain the difference between being overweight vs obese

Written by
Reviewed by
Dr Joseph Santos
FRACGP, MB.BS, B. Sci (Honors). University of Sydney

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

The terms ‘overweight’ and ‘obese’ are so often used together, you’d be forgiven for thinking they mean the same thing. But there is a difference between being overweight and being obese. Knowing about that difference can help you better understand how your weight may be affecting your health. It can also help you and your healthcare professionals to make informed decisions about your weight loss alternatives.

Obesity vs overweight definition

Overweight and obesity are both terms used to describe a body weight that is above what is considered to be healthy. A person with a body mass index (BMI) of between 25 and 29.9 is considered to be overweight. A person with a BMI greater than 30 is considered to be obese.

Measuring overweight and obesity in adults

From these definitions, you can see that the difference between being overweight or obese is related to your body mass index, or BMI. BMI is a measure used to classify overweight and obesity in adults around the world. Depending on your BMI, you may be classified as being underweight, a healthy weight, overweight or obese. Your BMI doesn’t represent exactly how much body fat you have or where it is distributed. However, it is an easy and inexpensive way to assess the risk your weight may have for your health. 

Another common method used to determine body fat levels and the associated health risks is measuring waist circumference. In women and men respectively, a waist circumference above 80 cm and 94 cm is associated with an increased risk of developing chronic conditions. A waist circumference of above 88 cm for women and 102 cm for men is associated with a substantially increased risk of developing chronic conditions. 

Obese VS overweight BMI

If your BMI falls between 25.0 and 29.9, you’re considered to be in the overweight category.

If your BMI is over 30, you’re considered to be in the obese category.

What is considered obese in Australia?

Australia uses the internationally accepted BMI definitions. In addition to being recognised around the world, these definitions are also used by researchers examining weight and health.

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How to calculate your BMI

If you know your height and weight, determining your BMI is relatively easy. You can calculate your body mass index by dividing your weight in kilograms by your height in metres squared (m2).

The body mass index formula is:

BMI = weight (kg) ÷ height2 (m)

For example, if your weight is 102kg and you are 1.68m tall.

Your BMI calculation would be:

BMI = 102 ÷ 1.682 = 36.14

Your BMI is 36.14.

What leads to excess weight?

Excess weight is often attributed to consuming more energy from food and drink than you use up with physical activity. This is an important part of the picture.

However, weight management is a complex medical issue and many other factors are known to contribute to people becoming overweight or obese. These include:


Your hormones are chemical messengers that communicate important information between the brain and the body. Several hormones play a key role in weight. Hormones are involved in regulating your appetite, metabolism and fat distribution. 

Numerous studies have linked hormonal imbalances with your likelihood of becoming overweight or obese. Furthermore, research also shows that weight loss leads to hormonal changes that encourage weight regain. This can create a vicious spiral that makes it extremely difficult to continue losing weight and keeping it off. 


Research shows that genes play a part in obesity. Genetic factors may contribute to your susceptibility to gaining weight. Genes can also play a direct role in the development of obesity in some disorders, including Prader-Willi syndrome (a genetic condition that hampers an individual’s ability to feel full). There are also rare genetic forms of obesity (known as monogenic obesity). 

Poor sleep

Studies have linked lack of sleep with being overweight or obese. A 2018 narrative review found that people who slept less than seven hours per night on a regular basis were more likely to have higher average BMIs and to develop obesity than people who slept more. This is partly because lack of sleep leads to hormonal changes associated with weight gain, such as increased levels of ‘hunger hormone’ ghrelin.

Environmental and social factors

Our environment and personal circumstances play an important role in our eating and physical activity behaviours and can contribute to the development of obesity and overweight. Some examples include:

  • The ready availability of calorie-dense and nutrient poor foods (statistics show Australians get about one-third of their energy from these so-called ‘discretionary’ foods)
  • Lack of access to easy or affordable physical activity programs
  • Advertising that promotes consumption of unhealthy foods, such as sugary drinks and fatty snacks
  • Oversized food portions
  • Lack of time to prepare nutritious, home-cooked meals (a 2017 study found eating home cooked meals more often was associated with a greater likelihood of having a healthy BMI and normal body fat percentage).

Health conditions

Some health conditions can lead to weight gain due to their effect on hormones. Examples include polycystic ovary syndrome, Cushing syndrome and underactive thyroid.


Certain medicines can also cause weight gain, including corticosteroids and some medications used to treat seizures and mental health conditions. 

Clearly, overweight and obesity can be caused by more than just eating more calories than you burn. Researchers are continuing to unravel how various factors interact and contribute to difficulties with weight management.

The health risks of being obese or overweight

Research shows that being overweight or obese increases your risk for developing numerous health conditions including:

  • heart disease and high blood pressure
  • type 2 diabetes
  • high cholesterol
  • some cancers
  • stroke
  • kidney and gallbladder disease
  • musculoskeletal problems, such as arthritis, gout, and joint pain
  • sleep problems
  • sexual health problems
  • difficulties with pregnancy and labour.

The risk for developing these conditions increases the higher the excess weight. Being obese or overweight can also make it more difficult to manage existing health conditions. 

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Losing 5% already helps

Research has shown that even losing 5 to 10% of your body weight can have numerous benefits for your health, including improvements in blood pressure, HDL (bad) cholesterol, blood glucose control, sexual dysfunction, polycystic ovary syndrome and menstrual irregularities.

Treatment for overweight and obesity

Fortunately, options are available for treating overweight and obesity. A great place to start is with healthy eating and more physical activity. However, not everyone has success with this weight loss method. 

If you’ve tried to lose weight but haven’t achieved the results you’d hoped for, there may be more happening than a simple energy in/out imbalance. It can be helpful to speak to a professional about other weight loss treatments.

Rosemary Health’s doctors have significant experience with helping people to lose weight. Our doctor-guided weight loss program combines proven treatments including 1:1 medical monitoring to help you lose weight effectively. Learn more or start your weight loss journey here.

Lose 10% weight, feel better
Doctor-guided weight loss. Free online visit.
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Lose 10% weight, feel better
Doctor-guided weight loss. Free online visit.
Start Online Visit
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