Jessie, a young American, is obsessed about losing weight. She is paranoid about having calories and often starves herself. Despite being dangerously underweight for her age, Jessie refuses to eat as she is terrified of the possibility of gaining weight. Which of the following disorders best fits the description of Jessie's condition?
A. anorexia nervosa
B. bulimia nervosa
C. schizophrenia
D. bipolar disorder
