Although there are genetic, behavioural, metabolic and hormonal influences on body weight, obesity occurs when more calories are taken in than are burned through normal daily activities and exercise. The body stores these excess calories as fat. But it is not always a matter of taking in and getting rid of calories, or leading a sedentary lifestyle. While these are the causes of obesity, there are others that cannot be controlled.
Obesity can cause more than just weight gain. The balance between calorie intake and energy expenditure determines a person's weight. If a person takes in more calories than they burn (metabolise), they gain weight (the body will store the excess energy as fat). If a person takes in fewer calories than they metabolise, they will lose weight.
Therefore, the most common causes of obesity are overeating and physical inactivity. Ultimately, body weight is the result of genetics, metabolism, environment, behaviour and culture. This amount of calories may seem high, but it can be easy to achieve by eating certain types of food. For example, eating a large takeaway burger, fries and a milkshake can total 1,500 calories, and that's just in one meal.
For more information, read our guide to understanding calories. Being obese or overweight means having too much weight and body fat. Being obese puts you in the higher weight range, above what is considered healthy. Being overweight also means that your body weight is outside a healthy range, but it is not as extreme as obesity.
Genetic changes in human populations occur too slowly to be responsible for the obesity epidemic. However, the way people respond to an environment that promotes physical inactivity and high-calorie food intake suggests that genes do play a role in the development of obesity. A couple of extra kilos of body fat do not pose a health risk for most people. But when people maintain a pattern of taking in more calories than they burn, more and more fat accumulates in their bodies.
The earliest sculptural depictions of the human body from 20,000-35,000 years ago show obese women. Your doctor will measure your height and weight to calculate your BMI and assess whether you are obese or overweight. Obesity is one of the leading preventable causes of death worldwide, with increasing rates in adults and children. People with Class I obesity and heart disease do not have higher rates of subsequent heart problems than people of normal weight who also have heart disease.
Find out here how making small changes to your children's diet and getting them active can reduce obesity and contribute to a much healthier life for your children. Your doctor can assess whether you are more likely to suffer health complications because of your obesity. In general, obesity is defined as a body mass index (BMI) equal to or greater than 30, which equals 30 pounds of excess weight. The World Health Organisation uses a classification system that uses BMI to define overweight and obesity.
Complications are either directly caused by obesity or indirectly related through mechanisms that share a common cause, such as poor diet or a sedentary lifestyle. Obesity is serious because it is associated with poorer mental health outcomes and lower quality of life. Studies have shown that, without intervention, children and adolescents with obesity are likely to remain obese into adulthood. Implementing multisectoral and impactful actions and strategies at different levels of the obesity causal chain as prevention and management of obesity can.
Despite the increasing prevalence of overweight and obesity in children, responses to address the range of the problem are inadequate in many countries. The Obesity Policy Action (OPA) framework divides measurement into "upstream" policies, "intermediate" policies and "downstream" policies. Obesity is also associated with leading causes of death in the United States and around the world, such as diabetes, heart disease, stroke and some cancers. Measuring fat around the waist is also a good indicator of the risk of obesity-related diseases.
