According to the University of Rochester Medical Center, morbid obesity is when a person has a body mass index of 40 or higher or is 100 pounds or more over ideal weight. For those with weight-related conditions, a body mass index of 35 or higher is morbidly obese.
The University of Rochester Medical Center states that being morbidly obese increases risk factors for diabetes, gallstones, sleep apnea and heart disease. It also interferes with normal functions such as walking and breathing and limits a person's ability to work. Normal body mass indexes are between 20 and 25, and doctors strive to help patients lose weight to reach these levels.