I have a son and I know for a fact he's very aware of what he's putting in his mouth , he tells me everyday the healthier choices he's been making at school. (his school now has chefs cooking and the food is much healthier and much more edible , last year all of the food was coming burnt and not many options).
I told him I'm proud of him for paying attention to what he puts in his mouth although he could stand to gain some weight, I still want the way he puts the weight on to be healthy.
He also see's the choices I've been making and he see's how my dad really abused his body over his lifetime and is now paying for it with his 3rd respiratory failure, dealing with diabetes, COPD (yes smoked for over 70 yrs) and so I keep telling him you have to take care of your body or you'll end up like your grandfather and he has a strong gene pool of diabetes with his both sets of grand parents having it and aunts and uncles.
So , very proud of him for making wiser choices! I think kids are more aware now, but everyone likes a little snack now and then too....