I recently read some cool med stories on that other site; your comment made me think of one in particular (an AMA I think) in which the nurse said that in regards to difficulty with blood-drawing/IVs/needles etc, obeast patients either have their veins under the fat or on top of it.  You can guess which is more difficult to draw from, though the nurse in question claimed it was especially rare to get one with veins above most of the fat.  Anyway, kinda rambled a bit there.