The pro is that it'll help save on medical costs in the long run, as healthy people are less likely to file claims, meaning it'll save the insurance companies on having to pay out money. If they offer incentives to the employee, then it'll be good for them as well, since being healthy usually = less time being sick, and if they have to pay less, then all the better (assuming the insurance company doesn't jack everyone's rates up of course, which they probably will).
The con is that this will either directly or indirectly cause a lot of invasion of privacy. If you're not living a healthy lifestyle, this will sort of force you into doing it. Yes, you could probably eat less twinkies and exercise more, but I'd imagine they'll go after smokers big time for stuff like this (Insurance company: "Smoking causes lung cancer, which means we don't want to pay for your lifestyle decision!"
, and may eventually also target alcohol drinkers as well (for you know, when that drunk driver hits you while you were jogging, and now you need to visit the hospital).And what about people with pre-existing conditions, such as being born with auto-immune hepatitis, or fibromyalgia, or sickle cell disease? Will insurance companies make some kind of excuse up to not cover those types of people, or raise their rates exponentially?
While some people may be fine with it, I'm guessing not a lot of people will be comfortable with the insurance company and/or the government forcing them to change their way of life/diet permanently.
