The extent to how much someone consumes should be in the control of themselves and not the government. It is their responsibility to be informed of the risks of eating too much. If people do not want to eat supersized amounts, they do not have to, but it should not be at the expense of the people who wish to eat that much.
In addition, everyone has their own metabolism, so what may be too much for someone may be the right amount for someone else. The people who can process higher quantities of food should not be penalized for their body's demands.