People seem more likely to graze these days, and to allow their children to graze on crisps, biscuits, sweets, popcorn, the list is endless.
I do think that is a big part of the problem and not just for children.
I don't see sugar as a huge enemy of the waistline per se - my mother would frequently cook jam roly poly, spotted dick smothered in syrup and custard, fruit crumbles, meringue filled with cream and fruit and then sprinkled with sugar, jam tarts, treacle tarts, etc but none of us were fat (in fact, as I have red hair and was so skinny, my brother used to say that from a distance I looked like a match!). However, there were no crisps in the cupboard, chips she saw as lazy food, pizza hadn't arrived on our shores and to even think of eating biscuits or sweets anywhere near to mealtime earned a stern rebuke - yet sugar did exist in quite large quantities by today's standards. My mum used to make pop from caly (sp?) crystals for us to take out with us. She would also make lemonade, orangeade, limeade from boiling fruit and sugar. However, sitting around doing nothing didn't enter our heads - we were out playing, climbing trees, riding bikes, roller skating, making go-carts and riding them downhill only to have to haul them back up again, swimming.
Life in general seems to have changed but, sadly, not for the better in many circumstances.