Final answer:
The severity of anorexia nervosa is classified based on BMI, with the categories ranging from mild to extreme, with extreme anorexia characterized by a BMI of less than 15.
Step-by-step explanation:
The severity of anorexia nervosa is typically classified based on BMI as follows:
- Mild: BMI ≥ 17
- Moderate: BMI 16-16.99
- Severe: BMI 15-15.99
- Extreme: BMI < 15
Morbid obesity is diagnosed when a person has a BMI ≥ 35 kg/m² with obesity-related health problems or a BMI ≥ 40 kg/m². It's important to remember that BMI is a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults.