Although there are genetic and hormonal influences on body weight, the bottom line is that obesity occurs when the body takes in more calories than it burns through exercise and normal daily activities.
The body stores these excess calories as fat. Obesity usually results from a combination of causes and contributing factors, including:
Inactivity: With a sedentary lifestyle, it’s easy to take in more calories than can be burned off through exercise or normal daily activities
Unhealthy diet and eating habits: A diet high in calories, eating fast food, skipping breakfast, eating additional calories at night, consuming high-calorie drinks such as sugary beverages and eating oversized portions all contribute to weight gain.
Environment: Quite simply, the environments in which people live, work and play has an impact on their health. People make decisions based on the community or environmental conditions of where they live. For example, in a community with few sidewalks, people may choose to walk less often because they don't want to walk in the street. Policies and the built environment of our communities, schools, and workplaces influence our decisions and behaviors. Because of this influence, it is important to create environments in these locations that make it easier to engage in physical activity and to eat a healthy diet.
Health conditions:* Obesity can sometimes be traced to a medical cause, such as Cushing's syndrome, polycystic ovary syndrome and other diseases or conditions. Some medical problems, such as arthritis, can lead to decreased activity, which may result in weight gain.
Medication:* Certain medicines may cause weight gain. These medicines include some corticosteroids, antidepressants and seizure medicines. These medicines can slow the rate at which the body burns calories, increase appetite or cause the body to hold on to extra water. All of these factors can lead to weight gain.
Age: As a person ages, they tend to lose muscle, especially if they’re less active. Muscle loss can slow down the rate at which the body burns calories. If calorie intake isn’t reduced, weight gain may occur.
Lack of sleep: Hormones that are released during sleep control appetite and the body's use of energy.