Recently I crossed the country with my parents to visit my grandma. She was born in the 1920s and spent a large part of her childhood in the Lower East Side, so it's quite a culture shock to visit her. In her case, it's not that you have to finish everything on the plate - it's that as soon as you finish one item, you're compelled to try three more. Or in other words, large quantities of food is the only form of hospitality she's really familiar with.
However this strategy arose, all her children have rejected it, which leads me to believe that these sorts of things can change quickly between generations. On the other hand, my parents are still erring on the side of "low-fat" style nutrition, even though I've told them repeatedly that it's been essentially debunked.
I wonder, what bad nutritional advice will I cling to desperately when I'm older?