Rhonda is a new mom who is experiencing many of the pressures of having a new baby. She has always been thin and was alarmed by the weight she gained during pregnancy. In order to take the weight off, she went on a crash diet and now weighs less than she did before pregnancy. She was inspired by this weight loss and has continued to restrict her calories. She is now at 80% of her expected body weight and has expressed to her husband that she is still too fat. She avoids eating with other people and tries to eat less than 500 calories per day. What eating disorder does Rhonda have?