And this is a good point about obesity being more than just a matter of personal responsibility:
Obesity is, at its heart, the result of many personal decisions. But the rise of obesity—across many countries and disproportionately among the poor—suggests that becoming fat cannot just be blamed on individual frailty. Millions of people, of all cultures, did not become lazy gluttons at the same time, en masse. Broader forces are at work. The government can try to influence them by discouraging overeating. But how?And more here, on how, unlike climate change or cigarettes, there is no single big solution to obesity; rather that the state will need to pursue a number of smaller solutions in schools and communities:
I would say that the article is worth reading throughout, but I suppose I've linked to most of it already.
For what it's worth, I don't think that big solutions to obesity are inherently flawed. The problem is that humans don't yet understand the areas of weight gain and weight loss well enough to design a policy that strikes at the heart of the obesity epidemic. We understand on a broad level that there are a number of factors that are correlated with weight gain (lack of exercise, fatty foods, overeating, etc...), and so we try to design policies to reduce these behaviors. But we don't fully understand, say, the biological process for how people lose weight.
I suspect that once we do understand this, there will be medications or surgeries that will do a better job of fighting obesity than any government policy. In the meantime, government will probably be reduced to tinkering around the edges, as it has been doing in recent years.