fellow blogger and a mother of a young recovered (i believe?) anoretic, came upon a sticky situation a while back. while shopping with her daughter, she noticed another girl - same age - shopping with her mother as well. the girl was frail and emaciated-looking (from what i gather of her post), which is enough to make your only-human mind jump to judgement as it is. the tip-off, however, was that she was apparently desperately trying to convince her mother that she was, in fact, a size 7 and that the dress she wanted would fit her body. long story short, she made the decision to pull the mother aside and offer her a little awareness. (click here for the whole story, in harriet's words.)
on more than one occasion, i have heard a close loved one of mine say, "i saw a girl in class/the mall/my gym today who looked so painfully skinny. she was obviously anorexic." this drives me insane, as i've openly voiced to the closest of these loved ones. first of all, you could be the closest loved one in the world - attending years of doctor's appointments, reading all the books amazon could offer, sitting through treatment intake after intake, even being talked to extensively by the person him/herself - but if you think all it takes is looking at a person to tell, you still really don't get it.
second of all, people who appear underweight to emaciated may be anorexic. they may also have thyroid problems. unexplained weight loss is also a symptom of cancer and arthritis. my brother became rather thin before he was diagnosed with juvenile diabetes. there's a reason treatment intakes usually last at least an hour. if all they had to do was see how a person looks, a small percentage of ED patients would be unpacked within 30 minutes and a much larger percentage would not even be accepted into the program. have you thought about that: how many people we probably walk by each day that look perfectly "normal" to us and probably have severe weight problems? i digress.
my feelings on the matter are as follows: i, personally, believe it's best not to say anything. please know, harriet, i respect your decision to do so. however - and i hope you do not take this to offense - i know that if i were that mother, i would have been very upset by a stranger overstepping my personal boundaries and making assumptions about my family's mental well-being. this is less towards you and more to the other parents who are wondering if and when they should step forward and say something to others, themselves.
the fact of the matter is that if someone is ignorant enough to miss that there is possibly a serious problem with themselves or someone they love, no stranger outside of that wall would certainly be able to break that boundary. it is really unfortunate how this disease goes unnoticed often for far too long, but it can rarely go any other way. people cannot seek help until they are willing to accept that they need it; this goes for both the patient and their families.
now, if this is a close family member of yours or a friend/friend's child, that's a different topic and that is based solely on your relationship with them. but for a completely random person in the store who has only known you for 30 seconds, tops, you don't know what is going on with that family or person. i mean, for all you know, that girl could have just been kicked out of treatment for the 6th time. it's far too large of an assumption to make with less than all the facts.