I’d take the long view here. When kids are little, and most easily influenced, just keep the junk out of the house. As kids get older, make sure you listen and respect their opinions, so they feel confident about their ability to make good choices. If they are well-educated—and good readers—they won’t be snowed by ads.
If you are too directive and controlling, you risk ending up with teenagers who will make poor choices (with food, alcohol, cars, dates etc) just to assert their independence.