Im not a big believer in the BMI scale, but if its saying you are under 20, you are too thin. I cant say bones sticking out always makes you too thin, as some people just naturally have bones that stick out. A friend of mine is a perfect weight and has a beautiful figure, but her clavical naturally sticks out a lot. It doesnt mean she is too thin. I agree with Irenes comment about the huge gap between the thighs - that never looks healthy in my opinion!
I couldn't give exact pounds because 120lbs would be too thin for a 6'4 male but not a 5'3 female, you know? So I guess it would be if the person is visibly unhealthy-they're emaciated, their bones are showing, their face is gaunt, their hair is falling out. Basically, too thin is when you go from healthy skinny to looking like I could snap you in half if I pat your back.
There are small things that bother me when a person tends to look underweight. The chick in your display looks too skinny to me. I don't like being able to see people ribs protrude drastically. As mentioned above, weird legs gaps are another thing. Same with really gaunt faces on top of that.
I can't tell in terms of weight, because you do get skinny people that are like that naturally, but for me as soon as the collarbone is showing prominently and a girl has a HUGE gap in between her legs, then I start freaking out about it.
when someone is underweight (meaning there too thin for there height and age) to me thats too thin. everyone is obviously going to be a different size because of their age, weight, height and genetics.
I can't really say because I have a thing for skinniness. But I think it's when you can see their ribs and pelvis bones clearly...
Depends on the person, their weight, their age, their height, their metabolism...etc etc...
when you can play a song in your rib cage and when an almond makes you feel full
When your so skiny you look sick , and you can see your ribs and other bones .
where you can see your rib cage, thats too thin. in my opinion.
there is no such thing as to thin
im under 20 and im fine :P