I know when I was at school, many girls were on free dinners. Their parents couldn't always afford to provide packed lunches and some of them would go hungry rather than eat the muck that the school kitchen served up as food.
Also, it's not just about diet. It's a whole lifestyle thing. During WW2, kids ate loads of reconstituted food - spam, snoek, powdered egg, etc. The diet was fatty and starchy, yet they never had the obesity problems then that we have now. I think that's because they had this attitude then of, 'if you want it, you have to go and get it'. These days it's more like, 'if you want it, ask and it will be given, on a plate, and all gift wrapped and tied with a pretty bow.
I watched that programme recently about ten kids who went on a WW2 style evacuation to a farm. They had to work, get their own food and learn to live without computers and mobile phones. It was amazing to see all these kids change from 'want it now' kids into the sort who put their heart, soul and back into everything they did, within the space of two weeks. At the end, their parents were commenting on how well they looked. And they weren't exactly eating pasta and salad every day.