Obesity is a leading risk factor of preventable illness and death in North America. In recent years, the number of overweight people in industrialized countries has increased significantly - so much so that the World Health Organization (WHO) has called obesity an epidemic. In the United States, over 50% of the population (about 150 million people) is overweight.
People who are obese are at a much higher risk for serious medical conditions such as high blood pressure, heart attack, stroke, diabetes, gallbladder disease, and different cancers than people who have a healthy weight.
Obesity occurs when your body consumes more calories than it burns. In the past, many people thought that obesity was simply caused by overeating and under-exercising, resulting from a lack of willpower and self-control. Although these are significant contributing factors, doctors recognize that obesity is a complex medical problem that involves genetic, environmental, behavioral, and social factors. All these factors play a role in determining a person's weight.
Recent research shows that in some cases, certain genetic factors may cause the changes in appetite and fat metabolism that lead to obesity. For a person who is genetically prone to weight gain (e.g., has a lower metabolism) and who leads an inactive and unhealthy lifestyle, the risk of becoming obese is high.
Although a person's genetic makeup may contribute to obesity, it's not the only cause. Environmental and behavioral factors also have a great influence. For example, consuming excess calories from high-fat foods and doing little or no daily physical activity over the long run will lead to weight gain.
Psychological factors may also foster obesity. Low self-esteem, guilt, emotional stress, or trauma can lead to overeating as a means to cope with the problem.