I think that banning the advertisements would definitely cut back on the junk food consumption in the country. The items will still be available for the individual, but they will not be flaunted. The temptation of seeing and hearing about these delicious foods will no longer be bombarding everyone at all hours of the day. I think banning the food itself would be wrong, but banning the advertisements is prudent.
While junk food is not part of a healthy diet, everyone wants to eat junk food sometimes. It can serve as comfort food. Banning advertisements on junk food goes against the idea of free speech.
Advertisements help with the economy, regardless of what the product is. It is not the choice of the government to ban ads related to junk food. I feel that it's the responsibility of the parent to teach their child healthy eating choices.
Because children are not held accountable for most of their choices, I do think that the government is justified in banning junk food ads aimed at children, in much the same way that they banned cartoons promoting cigarettes and alcohol. That said, I think ads aimed at consenting adults should still be allowed.