The government's will being theoretically derived from the collective will of the governed should not be used as a blanket appeal to authority. The people probably do not like all of their private communication being spied on by the NSA. That we've not yet elected officials and given them the power to stop such spying doesn't mean it's acceptable.
Moving on, the people should by default be free to make decisions that are not in their best interests. Just because you can't control yourself from eating candy doesn't mean my Right to Candy should be taken away as well.
Taking away liberty must be very, very carefully considered. What is the harm being prevented? What price is being paid to remove it? Seatbelts are a low cost to implement, a low cost to wear, and offer a high return of value in lives and health saved.
Banning imported food at tourist established is a much less obvious win. If I can't indulge in a sugary treat on vacation then when can I? That sounds like something the local agriculture industry is lobbying for more than anything. Who benefits the most from this change? Follow the money and I bet (heh) you'll find the big winners aren't the obese population.