How to tell if someone in my family has signs of possible eating disorder?

Questions... : Are they underweight for their height, but think they are fat? Do they obsess about gaining weight, think they are fat, although others tell them they r 2 thin. Have they stopped menstruating? Do they nibble at their food ; throw most of it away? If u r worried, it is worth consulting with a therapist who specializes in eating disorders it is hard to treat ; very important to take care of.