it's not just fitness, either.. it's pretty well documented that taller, stronger, more attractive men tend to be more favorably viewed in an interview setting, all other things being equal (even when being interviewed by another male.) women are also viewed more favorably if they are taller, thinner and mildly well-endowed. this stems from a psycho-sociological phenomenon known as the 'halo effect', whereby we see someone with certain positive characteristics like physical attractiveness, and begin to associate them with other positive characteristics despite any lack of supporting evidence (i.e. we assume that they are also trustworthy, intelligent, etc.)
in addition, studies have demonstrated that it can take up to six or seven pieces of contrary information to overturn a first impression in an interview setting. therefore, if the first impression that you convey is that you're tall, attractive and confident, you've already got a big leg up on the competition. and i don't think it takes too much imagination to extrapolate these findings to the clinical setting - those first few moments when your patients are sitting on that waxy waiting room butcher's paper and you pop your head in the door.
this mild rant has been brought to you by my bachelor's degree in psychology.. because that's about all it's good for.