I started thinking about this thread again when I was on a weeks holiday just now with some friends, a family with two kids. I love food, but it's fuel, and most fancy dinners are wasted on me. It was interesting watching how the kids ate. They're all quite active and we went cross-country skiing every day. My son likes to eat the same thing every day, but unless it's something he loves he needs pushing to eat. He just doesn't get hungry, it seems. And he hates trying new things. Our friends eldest eats what he's given and doesn't make a fuss. Their youngest, however, is hungry all the time. He's ten, like my son, tall for his age but is also getting quite chubby. He adores all food, and will eat anything not nailed down. Our friends try to limit his intake a little, but I notice that they mostly just delay him until we could all eat together, but they didn't seem to notice what he actually put in his mouth. For example - we got back from skiing and made a bowl of guacamole with chips to snack on before starting dinner. Most of us just dipped in and ate a little, their youngest almost sat in the bowl shovelling in the chips, then asked for something to drink and was given two full glasses of milk. Or he would always ask for, and be given, a second or third helping of dessert if there was anything left.
My point, I guess, was that even people living together doing the exact same activities and eating the exact same food can have very different attitudes to food. Some are indifferent, some eat obsessively, some wil home in on the most calorie-rich foods. I think these parents believe their kids "eat the same healthy food that they do", but haven't really noticed that that isn't the case.