I've been thinking a lot about this thread over the past few days. Someone posted early on about kids being skinnier in the 1970s. I'm was born in the late 70s, so grew up in the 1980s and was a very skinny child.
I've been thinking about what we ate as children, and from what I remember it certainly wasn't as healthy as the meals and snacks for today's children described on MN a lot of the time. There was lots of processed stuff: spaghetti hoops, fish fingers, angel delight, vitalite (remember that? Grim). There was a tuck shop at school during break and we all stuffed ourselves with crisps and drank Ribena until it came out of ears.
I think the elephant in the room is not so much diet or portion size as sedentary lifestyles and car-dependency. In the 1970s and early 1980s, it wasn't unusual to not have a car. Now - according to many posters on here - if you don't drive or have a car you're not a fully-functioning adult and must spend your life scavenging lifts. It seems utterly incomprehensible to some folks that it's possible to get around by walking, cycling or using public transport.
"Excersise" is going to the gym or playing sports, something removed from everyday life. I used to work in a second floor office with people who would spend every lunch break in the gym but would never dream of taking the stairs. They thought I was mad to walk a couple of miles to work and back everyday.
I feel quite passionate about this. If I'm honest, my diet is a bit crap. I like chocolate, beer and pizza, and I've never been on a diet in my life. I'm slim (UK size 10) because I walk everywhere. Usually pushing a heavy double stroller, or with the baby in a sling and running after the toddler.
I live in the US, in a city that is both one of the fattest and the least walkable. Sidewalks are in poor condition or non-existent (thank goodness for the all-terrain stroller). It's normal to get in your car and drive just two or three blocks and the amount of parking space needed to accommodate this dependency leads to massive urban sprawl, which makes it even less walkable! It boggles my mind that nobody here makes any of these connections!
I see some terrifyingly fat children here, and my heart breaks for them because they don't seem to stand a chance. They will most likely be obese and have health problems all of their lives.