it's interesting that you considering telling people how to live "for their own good" to be politically feasible. Authoritarians abound!
A person who eats healthy, exercises and takes care of themself ends up paying for those who don't.
On average, healthy people lived 84 years. Smokers lived about 77 years and obese people lived about 80 years. Smokers and obese people tended to have more heart disease than the healthy people.
Cancer incidence, except for lung cancer, was the same in all three groups. Obese people had the most diabetes, and healthy people had the most strokes. Ultimately, the thin and healthy group cost the most, about $417,000, from age 20 on.
The cost of care for obese people was $371,000, and for smokers, about $326,000.
http://www.nytimes.com/2008/02/05/health/05iht-obese.1.97488... (numbers from 2008)
The main factor as to why this is the case is important though. The longer you live the more costs you incur on the system because you end up getting another sickness which costs a lot more to treat, they specifically quote Alzheimers, than obesity and lung cancer.
One thing they did not take into account though is the lack of productivity i.e. the costs of being disabled (possibly b/c it is a dutch study using dutch data and parameters), in the USA diabetes is a disability and incurs significant other costs on the system which were not taken into account. It would be interesting to see what the comparisons would look like once that is taken into account.
But its certainly the case that smoking is much cheaper overall. It doesn't lead to disabilities and people die younger and incur far less costs.
[1] http://journals.plos.org/plosmedicine/article?id=10.1371/jou...
Even without a national health care system, taxpayers are paying for those who don't take care of themselves.