As a general rule, I do not have dark circles under my eyes or the sinus problems/posture problems it seems like a lot of us INTPs exhibit. Sometimes I have developed faint circles due to lack of sleep in short periods, but that is unusual to the point of being noticeable to others in my life. In full disclosure I do have pale skin (by choice and by sunblock) and require corrective lenses, which are also INTP-like characteristics. And I do have a tendency to stare off into space...and to seek out eye contact in conversations and hold it while sharing ideas...and I don't tend to physically withdraw into my body during social interactions. (Maybe learned through exposure.)
However, I have made a point out of eating lots of fruits and veggies, getting outdoors on a regular basis and (to a lazy and lesser extent) getting relatively regular physical exercise. Sometimes I have to remind myself to put down the book and go outside, because my first inclinations are usually to spend as much time researching/learning/considering as possible. But experiencing is a great thing, too...especially for us "living in our head" types...it can be just what we need to get out every now and then and to learn something in the material instead of the incorporeal.
Being into things like photography (I do a lot of detail studies of natural, spontaneous imagery), cooking (obsessed with learning recipes and compiling edible information) and Paganism (no dragons/crystals/deities for me; mainly pure natural cycles and experiences) have really counterbalanced those tendencies.
I don't think these or similar interests are so uncommon in INTPs, so I'm thinking that relying on those physical traits can prove to be misleading. Other introverted personality types would also share them, as might other thinking and perceiving types. (For example - some Idealist Counselors I know share those traits, due to hours spent indoors in serious emotive discussions, processing and ruminations.) Therefore I think it would probably be likely, but not absolute, that those physical traits may be found in INTPs. To put it in logical terminology - it would be a sufficient but not necessary condition. So it would therefore probably be a somewhat unreliable measurement most of the time.
This is an interesting thread, BTW.