Final answer:
Anorexia nervosa is the eating disorder characterized by extremely low body weight.
Step-by-step explanation:
Anorexia nervosa is the eating disorder characterized by extremely low body weight. People with anorexia nervosa consistently eat very little, have an obsessive fear of gaining weight, and have a distorted body image where they see themselves as fat even when they are very thin. This disorder is often associated with malnutrition, amenorrhea, and other serious health problems.