Anorexia nervosa (AN) is a disease of disordered eating that is characterized by self-starvation, often leading to extreme weight loss and difficulty maintaining a normal weight. Symptoms and behaviors of AN may include distorted body image, obsessive exercise, lack of menstruation among women, binge and purge eating behaviors, and intense fear of weight gain. Furthermore, people with AN are at a high risk of other mental disorders, such as depression and anxiety, and medical complications, such as organ damage, heart failure, and osteoporosis. Current treatments for AN include nutrition counseling, psychotherapy, and medication. Previous studies have suggested that certain medications usually used to treat schizophrenia, also known as atypical antipsychotic drugs, may be helpful in treating people with AN. Specifically, the atypical antipsychotic medications olanzapine and aripiprazole may be effective in improving overall symptoms of AN and in restoring weight to normal levels. This study will compare the effectiveness of olanzapine and aripiprazole in treating people with AN.