Slippery slope fallacy
What Chairmain said. There's a sight of difference between doing something which has the potential to result in injury and doing something which has been exhaustively documented as causing serious medical problems in all but a few rare cases.
Where is the effective difference between something that (over your entire life) with a probability of 50% causes medical expenses costing 10000$ and something that with a probability of 5% causes costs of 100000$¿ Just to list some things which I can imagine to be of similar costs per person doing them extensively:
- sun bathing
- mountain hiking
- climbing
- smoking.
So the argument that you would require bans on lots of other things still stands.
Doesn't follow. It's reasonable to drive/hike/whatever without expecting to be injured. It's not reasonable to start smoking without expecting to be injured. One is a slight possibility, the other is a near-certain eventuality. Hence why a car wreck is called an "accident" while emphysema from smoking is not.
That aside, you're also ignoring the obvious differences between things which are necessary (and slight) risks (for example, driving: there's a small chance that you'll be in an accident that injures you, but not driving is virtually impossible given the lives of most people); things which are hobbies that carry a possibility of injury (using your example, hiking in the mountains), but which cannot be rationally claimed to cause injury in the vast majority of cases; and habits which are (like hobbies) unnecessary, but which almost invariably lead to personal injury (smoking).
Since you enjoy pulling numbers out of your arse to support yourself, I'll answer with two things:
1. First, an equally-useless anecdote to make a point. Speaking from personal experience with my family, the medical costs of a smoker are far higher than those of someone who is injured in an accident.
2. Second, real numbers.
According to the U.S.
Federal Highway Administration, there were ~205 million registered drivers in the U.S. in 2009. In that year, according to the NHTSA, there were 33,808 deaths and injuries related to auto accidents in the U.S. I couldn't find numbers on accidents or injuries in crashes without fatalities, but that's workable enough.
That means that if you were a driver in the U.S. in 2009, you had (roughly) a
0.0164 % chance of being injured or killed in an auto accident.
According to the
CDC, roughly 43.8 million people in the U.S. are smokers. The average annual number of tobacco-related deaths in the U.S. in recent years is estimated to be around 440,000. This is a bit trickier to calculate, given that mortality due to tobacco use isn't instant. Still, it gives us a useful baseline of comparison.
The smoking population of the U.S. is only ~21% the size of the driving population, and yet smoking leads to 130% as many deaths as driving, using flat numbers.
I used smoking driving there both to make a point and because, for fairly obvious reasons, it'd be a major project to try and estimate the number of injuries and deaths due to relatively low-risk hobbies, much less leverage a comparison of average medical costs, and the ways in which obesity can affect health are more complex and unfortunately less documented than smoking.
Note that I'm not arguing against allowing people to overeat, I'm arguing against letting them do it and then have taxpayers front their medical bills when they're going in for yet another bypass operation. Of course, in a sense that presupposes that we have a sensible public health care system in the first place, so...
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And now it's time to eat lunch.