Is Obesity a Disease? Overweight vs Obese Explained
It depends who you ask. The World Health Organization calls obesity a chronic disease, and Australia's National Obesity Strategy 2022 to 2032 calls it "a chronic, relapsing condition". Formally, though, Australia lists obesity as a risk factor for other chronic diseases, not as a chronic disease in its own right (Australian Journal of General Practice, 2025). For adults, overweight is a body mass index (BMI) of 25 to 29.9, and obesity is a BMI of 30 or more.
This is general information, not medical advice. BMI and waist size are screening guides, outcomes vary between individuals, and a GP can look at your own health with you.
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Key Points
Obesity is excess body fat that increases the risk of health problems. Overweight is the range below it.
Australia's obesity strategy and the RACGP describe obesity as a long-term condition that needs ongoing care. Formally, Australia still lists it as a risk factor for other chronic diseases.
A newer approach separates clinical obesity, where excess fat already affects the body or daily life, from preclinical obesity, which carries future risk.
Fat around the waist raises health risk at any body size, so waist size matters as well as BMI.
Healthy eating, regular physical activity and enough sleep are central to managing obesity, and a doctor or nurse practitioner can talk through other options.
Is Obesity a Disease in Australia?
Obesity is defined as excessive body fat that increases the risk of health problems (healthdirect). Whether that makes it a disease has been debated for years. This is where the main bodies stand.
World Health Organization. It has defined obesity as a chronic disease since 1997, and many peak health bodies in the USA, Canada and the European Union have followed.
National Obesity Strategy 2022 to 2032. Australia's national strategy states that obesity is a chronic, relapsing condition, and that as body fat increases, our biology makes it more and more difficult to lose weight.
Royal Australian College of General Practitioners (RACGP). Its 2025 position statement calls obesity a chronic health condition that needs a long-term approach, and it expects periods of relapse and remission and lifelong management.
Australian Obesity Management Algorithm. This 2024 guide for Australian primary care describes obesity as a complex chronic disease with genetic, environmental, physiological and behavioural causes that requires long-term care.
Australia's formal position. In Australia, obesity is not nominated as a chronic disease in its own right, but as a risk factor for other chronic diseases. Many GPs see it differently: in a 2022 survey of 189 Australian GPs, 55.6% defined obesity as a chronic disease even without other conditions (Australian Journal of General Practice, 2025).
Why People Disagree
Supporters say that, for some people, a medical diagnosis can reduce the belief that their excess weight is entirely self-inflicted, and can change how the public and health services talk about blame (World Obesity Federation). Others argue that obesity is a risk factor rather than a disease, that the label would define a large share of the population as ill, and that it could put medical approaches ahead of behavioural and societal action. A 2019 article in the Australian Journal of General Practice adds that a disease label can bring some benefits, but it can also enforce social norms and entrench stigma.
The Australian Medical Association's 2016 position statement records the same split in Australia: some cite the international position that medicalising obesity will improve treatment, and others argue that it does not meet the definition of disease.
Clinical vs Preclinical Obesity: A Middle Ground
In January 2025, the Global Commission on Clinical Obesity, published in The Lancet, proposed two categories and asked doctors to look beyond BMI. Its chair said the question of whether obesity is a disease presumes "an implausible all-or-nothing scenario". The commission's recommendations have been endorsed by 75 medical organisations around the world.
Clinical obesity. Excess body fat plus signs or symptoms of obesity-related organ dysfunction, or limits on daily activities. The commission lists 18 criteria for adults, including breathlessness and knee or hip pain.
Preclinical obesity. Excess body fat with no signs of organ dysfunction and no limits on daily activities. It points to future risk rather than current illness.
To confirm excess body fat, the commission recommends BMI plus at least one other body measure (such as waist circumference or waist-to-height ratio), two body measures, or a direct body fat scan. In March 2025, an Australian GP noted that guidelines for weight loss medication and surgery still use BMI.
Overweight vs Obese: The BMI Classes
Overweight and obesity both mean carrying too much weight in the form of body fat, and obesity is the highest range above what is considered healthy. BMI is your weight in kilograms divided by your height in metres squared. These are the classes for adults.
| BMI | Classification |
|---|---|
| Under 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight range |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity class I |
| 35.0 to 39.9 | Obesity class II |
| 40.0 or more | Obesity class III |
The healthy, overweight and obesity classes are those used in the Australian Obesity Management Algorithm (2024). Healthdirect gives the underweight range and calls a BMI of 35 or higher severe obesity.
As a worked example, a person who is 1.70 m tall has a height squared of 2.89. At 85 kg, their BMI is 85 divided by 2.89, or 29.4, in the overweight range. At 90 kg, it is 31.1, in obesity class I. This is arithmetic only and says nothing about that person's health on its own.
BMI can be less accurate for people under 18 or over 65, during pregnancy, for elite athletes, and for people of Asian or Polynesian background. In Asian populations, a higher risk of diabetes and cardiovascular disease begins at a BMI as low as 23 (Better Health Channel). Children use separate BMI charts for their age and sex.
In 2022, 65.8% of Australian adults were overweight or obese, made up of 34.0% overweight and 31.7% obese (ABS National Health Survey). The obese share rose from 27.5% in 2011-12, and men were more likely than women to be overweight or obese (71.2% compared with 60.5%).
Percentages are as published and do not add to exactly 100.
Why Waist Size Matters: Abdominal Obesity
A waist measurement shows where fat sits, which BMI does not. Fat around the abdomen, regardless of body size, makes some obesity-related conditions more likely, and the Better Health Channel calls waist circumference a better predictor of health risk than BMI. A waist of 94 cm or more for men, or 80 cm or more for women, means an increased risk, and 102 cm or more for men, or 88 cm or more for women, a substantially increased risk. Australian obesity guidance uses the higher pair of cut-offs to define abdominal obesity.
In 2022, 67.9% of Australian adults had a waist measurement that put them at increased risk of disease (ABS). A larger waist is a guide to internal (visceral) fat around the organs, explained in what visceral fat is and why it matters. For steps that help, read how to lose belly fat and the best exercises for belly fat.
Why Australia Treats Obesity as a Health Condition
Whatever the label, Australian health policy treats obesity as a serious health issue, for these reasons.
Health risks. Overweight and obesity raise the risk of heart disease, stroke, type 2 diabetes, some cancers, kidney disease, high blood pressure, joint problems and sleep problems. The higher the excess weight, the higher the risk.
Shorter lives on average. People with a BMI of 30 to 35 die 2 to 4 years earlier on average than people at a healthy weight, and people with a BMI of 40 to 45 die 8 to 10 years earlier (Department of Health).
Disease burden. In 2024, overweight and obesity overtook tobacco as the leading risk factor for disease burden in Australia, at 8.3% of the total (Australian Institute of Health and Welfare).
Many causes. Obesity is complex. Genetics, medical conditions, some medicines and metabolism, along with sleep, stress and where you live and work, all influence the chance of living with obesity, and some of these are beyond a person's control.
Stigma. Weight bias leads to people being treated differently or unfairly because of their weight, including in health care. Past negative experiences and fear of weight shaming make people living with obesity less likely to take part in health checks and screening, so some present when disease is more advanced (RACGP).
Obesity has been an Australian National Health Priority Area since 2008.
Healthy Diet, Physical Activity and Medical Care
Healthy eating, regular physical activity and adequate sleep are central to managing obesity. Losing as little as 5% of body weight can bring health benefits, such as a lower risk of heart disease or type 2 diabetes, and healthdirect advises focusing on behaviour change and improved health rather than weight loss goals. Outcomes vary between individuals.
Eat a healthy diet. The Australian Dietary Guidelines recommend a wide variety of nutritious foods from the five food groups every day: vegetables and legumes, fruit, grain foods (mostly wholegrain), lean meats and alternatives, and milk, yoghurt and cheese or alternatives. To understand the energy side, read what a calorie deficit is and how many calories a day you may need.
Stay active. Australia's physical activity guidelines for adults recommend moderate to vigorous physical activity for 30 minutes or more on most days, and muscle-strengthening activities on 2 or more days a week. For ideas, read how many steps a day can support weight loss.
Set a realistic goal. To work out progress as a share of your starting weight, see how to calculate your weight loss percentage, and for a full plan, read how to lose weight.
For people living with obesity, treatment may also include weight loss medication or bariatric surgery. Weight loss medication is used while reducing kilojoule intake and increasing physical activity, not instead of them. It has side effects and can be harmful for some people, so it is a decision for a doctor or nurse practitioner after an individual assessment. A dietitian, exercise physiologist or psychologist can also help. To learn more, read how medical weight loss programs work.
Alongside a healthy diet and physical activity, Burst Health provides medical weight loss plans online for adults living with obesity, or overweight with related health risks, reviewed by an Australian-registered doctor or nurse practitioner: check whether you are eligible.
Frequently Asked Questions
Is obesity a disease, yes or no?
Sometimes, under the newest approach. A 2025 global commission set criteria to tell obesity as a risk factor apart from obesity as an illness in itself. Excess body fat that already affects the organs or daily activities is clinical obesity. Excess body fat without those effects is preclinical obesity, which points to future risk. A GP can check which applies to you.
When did obesity become a disease?
There is no single date. A World Health Organization consultation classified obesity as a disease in 1997, the American Medical Association followed in 2013, and the World Obesity Federation published its position in 2017. In 2025, a global commission set out criteria for clinical obesity in The Lancet.
Is it okay to be overweight but not obese?
It depends on your own risk. The link between overweight and illness is not definite for each person, but risk rises with BMI and waist size across the population. Fat around the belly carries more risk at any body size. Some researchers suggest a BMI of 22 to 26 suits Australians over 70. A GP can assess your own risk.
What causes abdominal obesity?
Abdominal obesity means extra fat around the waist, with a waist measurement above the substantially increased risk cut-offs listed above. Internal belly fat builds up when you eat more energy than you use and do too little physical activity. Older men, women after menopause, people with a genetic tendency and people who drink too much alcohol are more at risk.
Medical weight loss plans, online
In three steps.
- 1Answer a quick questionnaireOnline, no appointment, no in-person visit.
- 2A practitioner reviews itAn Australian-registered doctor or nurse practitioner decides whether treatment is suitable for you.
- 3Start your planIf treatment is suitable, you start your plan with the practitioner supporting you throughout.
References
Australian Government Department of Health, Disability and Ageing. About overweight and obesity.
Australian Journal of General Practice. The politics of disease (October 2019).
RACGP newsGP. World experts urge overhaul of obesity definition (January 2025).
RACGP newsGP. Australia's new leading contributor to burden of disease (December 2024).
Healthed. What will new diagnostic criteria for obesity mean in practice? (March 2025).
Australian Medical Association. Obesity, 2016 (position statement).
Australian Bureau of Statistics. Waist circumference and BMI, 2022.
healthdirect. Body mass index (BMI) and waist circumference.
healthdirect. How to reduce excess internal body fat (visceral fat).
Better Health Channel (Victorian Government). Body mass index (BMI).
Eat for Health (NHMRC). Australian dietary guidelines 1 to 5.
This article is general information only and does not replace individual medical advice. Please speak with a registered Australian healthcare practitioner about your own circumstances.