According to Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention (CDC) in the United States, the number one health problem in the United States is the new epidemic of obesity. What does it mean to be obese? Most doctors and researchers use the body mass index, or BMI, to determine whether someone is the overweight or obese. The BMI equals a person's weight in kilograms divided by a square of the person's height in meters. A normal BMI is between 18.5 and 24.9. A person with a body mass index of 25.0 to 29.9 overweight, while a person with a BMI of 30 or above is said to be obese.