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’ve 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?