Use the case of smoking or obesity as the focus in explaining why health and illness are as much a societal and cultural issue as they are medical.

That is a great request. There are always cultural and societal variables that are important. If you consider smoking, society, insome ways, encourages it, at least in the past by advertising and commercials. We don't see this today as much, but still smoking and the connotations that it is "cool" to smoke is still in movies. Also tobacco companies are very powerful and have a lot of clout in politics.

As for obesity, just consider all the restaurants in America that serve unhealthy foods - pizza hut, burger king, etc. They are relatively cheap. Try to get a good salad and it is hardly affordable! What does society say about this?