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 condition, 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.
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.