It doesn't have a detrimental effect on the medical system though.
It shifts the cost in time and then we can't see the counterfactual of the drinkers and smokers not being dead younger than what they would have.
You can't see how much the current 30 year old marathon running vegan is going to cost the system 50 years in the future compared to the smoker who needs treatment in the present. We pretend that the marathon runner is somehow saving the system money over the sum of their lifetime when in reality the one who is saving the system money is the one who dies younger than they would have. The one who prolongs their life longer than it would have been is the expensive one to the system. This is patently obvious if you spend any amount of time thinking about it.
Of course, no one is going to promote a type of libertine lifestyle as a way to save the healthcare system money. The thought is so unpalatable that we pretend the opposite is true.