I do believe universal health care is a human right, and that societies with universal plans tend to have better health overall. I believe we can also create incentives for people to live healthier lifestyles and to maintain a healthier Body Mass Index too. We can offer tax credits, subsidies for workout clubs or cheaper insurance rates, even within a universal government-administered system. Studies have shown that people tend to respond better to such incentives anyway, rather than punitive measures such as being excluded from health care.
Beyond such incentives, I don't think you can really control what people do with their lifestyles, and I also don't think that diminishes their right to have affordable access to quality health care. Perhaps more of an effort to regulate food production, especially in the fast food industry and in food processing, can have more of an effect.
In my opinion, if the government is going to fund healthcare for anyone, it must fund it for everyone (in some age range or income range or whatever). I do not think it can make distinctions of the sort that you are talking about here.
My reasoning here is that it is too hard to determine who is worthy and who is not. What if you live an unhealthy lifestyle--you have way too much stress and you do not eat healthily? Deny you coverage because it's your own fault. But what if you have all this stress and bad eating habits because you are working two full-time jobs to try to support your family? Now what? How can the government decide who is worthy of care and who is not?