They also get to hear about the surgeries that result purely from poor diet and lack of exercise. And throw in the various health issues in family history that can be lessened through eating/not eating certain foods. We're killjoys, what can I say!
The thing is that now they're aware, so it doesn't have to be said everytime they open their mouths. And they learn moderation. Like my son just got Easter candy from his grandma and asked if he could eat his jellybeans and I said "sure, just don't eat the whole bag in one sitting" (though it is what I assume to be a single serving bag). He opened them, ate maybe 4, put the rest in a ziploc. He could have had many more than that for all I cared but he's heard before that candy is an occasional item because it isn't good for you so he is learning to ration. I'm sure he'll eat more later, but so far no binging or hoarding when they see junk.
So hopefully the ideas sticks and while they are bound to eat more junk than they should during certain years of their lives, at least their early years will be primarily healthy. And healthier in not just their consumption, but things like getting fewer x-rays at the dentist because they are "low risk", according to their ped dentist, because they don't regularly drink juice, soda, or eat a lot of candy or soft, sticky foods.
And again, maybe we're just lucky, but we don't see soda offered to kids in our regular activities. My 7yo was at a birthday party today and when I picked him up I checked the beverages offered solely because of this thread: lemonade, water, apple juice, and grape juice. My oldest was camping with her Girl Scout troop all weekend and the troop leader brought up individual waters, a large water "keg" and a 2nd keg for lemonade. No sodas at either event.