Obesity is defined as an excess of body fat and a body mass index, or BMI, of over 30. Morbid obesity refers to a person who is 50-100% over normal body weight, more than 100 pounds over a normal weight, or has BMI of 40 or higher. Morbidly obese people have a body weight that interferes with their general health and everyday function. Diet, age, gender, genetics, lifestyle behaviors, physical activity, illness, medication, and psychological factors such as boredom, sadness, and anger all play a role in obesity.