While this is, of course, a matter of opinion, my own feeling is that the government should not do this. It would be impossible to enforce and it would restrict our personal freedoms without doing much good. There are better ways to combat obesity.
In a democratic society like our own, we should be responsible for our own actions. We should be given the information that we need, and then we should be allowed to live our own lives as we like. If we do things that are bad for us, we should suffer the consequences.
What this means is that the government should not try to do things like the New York City ban on large soft drinks. What it should do is to educate people (as it already does) as to what causes obesity. In addition, it should allow insurance companies to charge higher premiums to people who are not in good shape.
It should be our choice to drink what we want. If we can drink soda and stay healthy, fine. If we want to drink soda even though it makes us unhealthy, that should be our choice so long as we are willing to pay for the consequences.
In addition, it is highly unlikely that regulation would work. If we ban large sodas, what is to stop someone from buying two medium sodas? It really seems pointless.
The government needs to put more responsibility on the people rather than trying to protect them from making bad choices.