Obesity is a result of an individual consuming more calories than she or he burns. Genetic, environmental, psychological, and underlying medical problems may all be factors that lead to obesity. Underlying medical conditions may include hypothyroidism, Cushing’s syndrome, depression, and certain neurological problems that can lead to overeating. Drugs, such as steroids, used to treat certain medical conditions may cause weight gain, too. Scientific study has indicated that obesity is linked to heredity. However, since family groups also share the same basic diet, it is difficult to separate genetics from environment. The average American diet tends to include many foods that are high in fat. The standard portion size for many foods has increased over the past several years. “Super-sized” portions available at fast-food restaurants have more calories. This diet coupled with a lack of physical activity leads to obesity. In addition, many people overeat in response to negative emotions such as sadness, anger, and boredom.