to a pretty big degree, IMO. I mean, that's how all insurance works. I've never caused a car accident in my life, I haven't broke the deductible on my healthcare in a decade, Dont have any kids, not likely to die anytime in the near future. Yet I pay thousands a year for all that insurance so that people can drive like idiots, go to the doctor constantly, and cr@p out kids like their life depended on it.
Sure, you don't pay for the uninsured fatty to get regular (cheap?) checkups, but you ARE already paying for him to go to the ER when he actually has a heart attack. Which maybe could have been prevented with regular care and medication? Some certainly would be, but I haven't seen any statistics on how much emergency medicine is likely to be prevented by more preventative care.
There's also another thing to consider. I can't remember the number, but I've seen it reported in the news that millions of the uninsured can afford it, they just choose not to. Common sense says that if you can afford insurance and forego it, you're probably pretty healthy. If those people are required to get insurance that is an aspect that will actually reduce insurance premiums (not to say that it's enough to cause a net reduction).