A 46-year-old woman with a BMI of 35 reports episodes of feeling "out of control" with eating. She says that during these episodes, she eats an extremely large quantity of food in a short period of time. She eats quickly and past the point of being full, which leaves her feeling physically uncomfortable. After these episodes, she feels ashamed. She has been hiding this behavior from her friends and family for about 4 months. What is the most appropriate diagnosis?