Obesity is a chronic disease. And just like many other chronic diseases, it develops over time from a combination of biological, psychological, and environmental factors.

But what is it that makes people gain weight? Why do some people develop obesity? There isn't just one specific thing. As you can see in this video, obesity is far from simple.

The causes of obesity are complicated and vary from person to person. These include:

• Genetics. Tiny genetic variations can make you more likely to carry weight and develop obesity.
• Hormones. The balance of hormones in your body can affect your appetite and food choices, as well as how much energy you use.
• Stress. High stress levels can make you overeat and gain weight.
• Sleep. How much and how well you sleep can affect your hormones, which can make you eat more food.
• Medications. Some medicines can increase your appetite or affect your metabolism so that you gain weight.
• Environment and socioeconomic status. Where you live and your access to different kinds of food is related to developing obesity.

There are so many reasons for obesity. And once a person has developed obesity, it's not easy to manage weight and keep it off. Because of this, it can be hard to find the right way to treat or manage obesity.
 

Although the causes of obesity are complex, there are people who think that obesity is only a matter of lifestyle. It's a common belief that if a person only ate the right food and exercised in the right way, they wouldn't gain weight or develop obesity.

On some level, it is true. Losing weight does depend on the balance between how much energy you have (from the type and amount of food you eat) and how much energy you use (by exercising or carrying out normal body functions like breathing). But, this dramatically simplifies obesity. It's also hurtful to people who are affected by obesity. Eating less and moving more isn't always enough to manage weight and prevent you from developing obesity.

For Vicki Mooney, a mother of three living in Spain, the reasons for obesity seemed out of her control. “I go to the gym, I eat very small portions, I do yoga. But I am still overweight. People will say to me ‘eat less, move more, and you will be fine’. But it's really not that simple”.

Anyone who's also tried to manage weight without much success knows it far too well. You can try to be consistent and do all the right things to manage obesity and still struggle. Losing weight is hard. Keeping the pounds off after you lose weight is even harder.
 

Thankfully, the science shows that obesity is a manageable disease with many causes. More and more healthcare professionals recognise that obesity is a disease. At the same time, they're working to remove the stigma associated with obesity to make sure that people living with obesity get the help they need. In this video, medical experts from around the world talk about the reasons for obesity and other misconceptions. Play the video to hear their discussions about:

• Why should obesity be considered a disease?
• Why are many people skeptical that obesity is a disease?
• Why do people struggle to maintain their weight loss?
• What would be the benefits of recognising obesity as a disease?