Obesity can seem straightforward to explain. If a person consumes more calories than they need, they gain weight. But the real explanation is not that simple. And it is about more than weight.

Obesity is a complex chronic disease, and losing weight is not just a question of eating less and moving more. In fact, obesity can be influenced by genetics, physiology, environment, job and education, and what is going on in the brain.

Understanding these factors is critical, because obesity is associated with other diseases, including type 2 diabetes, heart disease and certain types of cancer. Not to mention the stigma and bias millions suffer every day.

But with the right care, people with obesity can achieve sustained weight loss that really makes a difference to their health.

Today we know that obesity is a serious chronic disease, not simply a matter of effort. 

Together with our partners, we are committed to driving change in how the world sees, prevents and treats obesity. As leaders within the science of obesity, we are working to make obesity a healthcare priority, defeat stigma and support better access to evidence-based care.

Scientific and medical experts are increasingly recognising obesity as a serious chronic disease. While this may come as a surprise to some people, it is a big relief to others, especially those living with the disease.

But why is obesity a disease and not simply lack of willpower or a matter of lifestyle? Part of the answer lies in the fact that there’s more to obesity than you can see. Its causes are multiple, from genetic disposition to brain chemistry, it is not an easy disease to treat.

The good news is that obesity is a manageable disease and people who live with it are getting improved treatments and programmes to support their health and wellbeing. But there is a lot of work still to be done to increase awareness, fight stigmatisation and discrimination.

In the video above, meet people living with obesity and hear first-hand about the emotional burden of stigma and bias, seen through their eyes. 

Obesity is influenced by many factors both inside and outside of the body. A person could be born with a tendency to put on weight. Just as someone is born with a particular eye colour.

There is also the physiological aspect. When a person eats, hormone signals from the stomach and gut are translated into feelings of reduced hunger and increased satiety. This controls a person's food intake.

During weight loss, the level of hormones can change in an attempt to regain the lost weight. As a result, studies show that only about one third of people successfully maintain their lost weight.

Many aspects of a person's general well-being, environment and lifestyle can also cause weight gain. Where a person lives and the culture that surrounds them can also influence the risk of developing obesity.

So, although many people with obesity believe they should be able to manage their weight on their own, it is not that easy. 

To understand obesity, we must understand what is going on in our brains. It seems our bodies are hard-wired to hang on to those extra calories, probably because for thousands of years, it was a basic survival mechanism.

Therefore, people living with obesity struggle to lose weight. Their bodies' programming works to get them back to their original starting weight. In the brain, it's as if there is a switch that tweaks a person’s energy expenditure until they have regained the lost kilos.

We are trying to pinpoint where exactly in the brain such a switch could be located and exploring whether it is something we could address with a medicine. So that one day, we might be able to help people with obesity to ‘reset’ their weight to a new, healthier starting point.

If we succeed, we could help millions of people.

Read more about our mission to defeat obesity

Obesity illustration displying a city outline.

We aim to be the leading force in the science behind obesity.

We pay great attention to the natural GLP-1 hormone. We are uncovering more and more about the role this naturally occurring hormone appears to play in achieving successful weight loss. For example, after a person has finished a meal, the GLP-1 molecules in the body affects their feelings of hunger.

For several years, our scientists have studied how synthetic GLP-1 molecules can be used to suppress appetite or increase energy expenditure. And we will continue to examine how GLP-1 can spur long-lasting weight loss.

Currently, we are researching into the following areas:

  • 20% weight reduction
  • Cardiovascular benefit

Learn more about our ambitious R&D pipeline.

Abigail, 29, lives in West London

'Obesity – The Truth from Within' puts a lens on the personal stories shared by people living with obesity, a chronic disease that affects more than 764 million people globally.

Their efforts to manage the disease and shake off the burden of stigma are highlighted through a series of intimate portraits captured by photographer Abbie Trayler-Smith. 

Hear the stories from five people living with obesity

Join us as we break new ground, changing the way the world sees, treats and prevents obesity.

Learn more about our career opportunities