On one hand, I think the government does have a job to intervene when negative externalities affect society (like obesity has). On the other hand, as this story demonstrates, they clearly suck at intervening.
On a personal level, I don't care what McDonalds does because I don't take my kids there (I have 3 kids under 7). But I care about obesity being a drain on society and a healthcare issue we all have to share. McDonalds, well, they care about profits.