Dean Karnazes at 5'8, 155lbs(ish) is one of the few well-known ultra distance-type guys who springs to mind for me as having sort of a normal, healthy looking build. Obviously these guys are no more interested in building aesthetically pleasing physiques than BB'ers are in performing mind boggling feats of endurance. Even at levels waaay below that of the Tour, it's amazing the amount of chronic health problems serious athletes struggle with.
Rassmusen seems like a somewhat extreme case, as some have already mentioned. Visually the extremely pale skin and the discolored spots on his chest contribute to the appearance of illness. However I think that the Tour is hard to the point of being actually severely traumatic to all the body's systems. That said, you have to admire the will and determination.
Anything, taken to it's extreme, becomes harmful.