The way to resist the effect of obesity on healthcosts is to attack its root causes: the overuse of sugar, the promotion of shoddy advice, the lack of time for people in poverty to prepare food for their families etc. Overwraught and moralistic plans (but what if their was a fat tax?
) have no real effect at the end of the day, beyond making people feel superior.
Sure, we can go down the 'attack teh FATTIES lol!!!!' route, but it is rather stupid at the end of the day. First it boosts the craven and idiotic ideology of 'fat=unhealthy, skinny=healthy' (which is largely a construct of the insurance industry, rather than medical science). I, for example, have exactly 'correct' BMI but I have no doubt that a lot of people who cross the threshold of BMI are very much healthier than me.
It is very much more efficient to treat people the same, however much you feel they 'did this to themselves'.