Final answer:
The major health complication associated with intractable anorexia nervosa is the risk of heart failure, which can be fatal. Anorexia nervosa leads to severe health issues like loss of bone mass, muscle weakening, and particularly, cardiovascular problems that can hasten death if left untreated.
Step-by-step explanation:
The major health complication associated with intractable anorexia nervosa is significant risk of heart failure, which can lead to death. Due to chronic malnutrition and severe weight loss, individuals with anorexia nervosa may experience a range of serious health issues. These include loss of bone mass, weakening of the heart and other muscles, abnormally low heart rate and blood pressure, weakness, dizziness, fainting, and amenorrhea in females. Without treatment, these conditions can result in grave consequences, highlighting the critical importance of addressing this eating disorder promptly and effectively.