It's no different than refusing to hire someone over weight or who drinks too much caffeine.
@tapeworm :
I wouldn't be too sure people are not being hired due to obesity. More and more health care facilities are requiring physicals for new hires. Once again, I have a feeling that it isn't so much the employer as it is pressure from their insurer. And of course both probably have enough high dollar attorneys to ensure against discrimination cases. If it is the insurers who are requiring these things, you know they are ready to fight any discrimination cases against them.
BTW, I'm NOT sticking up for them. I've just seen this in action.