The parent tells the nurse, “Every day, for the past three o…

The parent tells the nurse, “Every day, for the past three or four months, I find a lot of empty food wrappers hidden in my teenage daughter’s bedroom. After a meal, she runs right to the bathroom and stays there for at least 20 minutes. I also noticed she is buying laxatives every week.” Based on this information, which of the following does the nurse suspect is the most likely cause?