What is obesity

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What is obesity

What is obesity?

Obesity is a serious chronic disease associated with having excess body fat to the extent that it may have a negative effect on your health. Obesity is complex because it is influenced by a combination of many factors both inside and outside your body1,2.

Watch a short animation video outlining the complexity of obesity as a chronic disease.

Factors influencing obesity

The rise of larger meal portions, physical inactivity   due to excessive screen time and easy access to   unhealthy foods are just some of the many   environmental factors that can contribute to you    developing obesity3.
Where you live and your income also influence your risk of developing obesity4. For instance, if you have a high socioeconomic status you are more likely to have obesity if you live in a lower income country, but less likely if you live in a higher income country5.


Obesity is generally understood to develop because of an imbalance between energy consumed as food and the way the body uses this energy for things like physical activity. Any energy the body does not use is then stored as fat6. But this process is complex: appetite and energy expenditure are regulated by the brain based on signals from many parts of the body, including the gut, pancreas and fat-storing tissues7. Additionally, other biologic factors, including certain medical conditions, can have a negative influence on this process.

4  Emotional
Stress, trauma, and mental health problems can sometimes lead to overeating, which may contribute to the development of obesity8,9.

Some people can also be genetically predisposed to obesity, so your family history and ethnicity can also affect your risk of developing the disease10.

The science behind obesity

The science behind obesity is complex, and the underlying cause of the disease – an energy imbalance between food consumed and the energy used – is just one part of the story.

Scroll through this interactive infographic to learn more about the internal and external factors that can influence your chances of developing obesity.

Explore the science


The science behind obesity

Measuring obesity

Obesity is classified as having a Body Mass Index (BMI) of 30 or higher. BMI – or your weight in kilograms divided by the square of your height in metres11 – may be used by your healthcare professional to see if you are the right weight for your height, and can be a useful tool for identifying obesity. Many people affected by obesity are not even aware that they are living with it.