Well, it seems they've got their wish - everyone arguing with everyone else about who is "worthy" of treatment. It is the same method of dividing people that they use when cuts to welfare and public services are made.
As an example, Hattiehelga says "start charging health tourists and those who have not paid a penny into the system". Apart from emergency treatment, people from non-EU countries who want to access the NHS have to pay. Presumably those who haven't paid a penny into the service are either children, permanently unemployed people or people unable to work through disability or chronic illness. I certainly wouldn't deny any of these health care.
Much human behaviour carries a degree of risk, including - as anniebach said those who engage in sports, especially contact and extreme sports, and those who drive, ride motorcycles or bicycles. Being overweight is a risk factor but it is not inevitable that people who are overweight will have a bad outcome. A friend of my mum's - a lady in her early 80's - was fairly overweight when she had her hip operation. This was partly caused by the fact that her painful hip and a heart condition stopped her riding her bicycle and walking as much as she used to. However, she has recovered very well from the operation and is now able to walk more.
I agree that people with addictive behaviour - whether it be smoking, drinking, eating, etc. - should be encouraged and helped to give up their addictions but I don't think it is right that they should be denied treatment unless there is, in the unanimous opinion of the relevant doctors, a very high risk of danger to the patient or of a very poor outcome generally. I don't think cost should come into it.
Several famous and successful sportspersons have been smokers by the way. And jockeys tend to smoke to keep their weight down.
I do think that so far as weight is concerned there are some people who are just unfortunate in putting on weight very easily. (and I'm not saying that as a defence for myself - I am overweight but not significantly so). It is easy to be smug and self-congratulatory if you are one of those people for whom weight has never been a problem. I also think that these days a lot of people have a very unhealthy relationship to food - with increasing numbers of people being overweight at the same time as increasing numbers of people suffering from anorexia and bulimia. So it is a complex issue with no simple answers.