> A big part of the story, as she tells it, is that American kids used to be hungrier at mealtimes

This is putting it extremely mildly. There are entire groups of nutritional health concerns that virtually nobody knows of today that were common at the turn of the 20th century. Rickets, Pellagra, Goitre, Xerophthalmia, etc.

All of these are caused by poor nutrition. Children back then were much smaller, again, due to lack of food and poor nutrition. During the world wars, double digit percentages of recruits were rejected due to being malnourished.

> Children in the 19th century happily consumed wild plants and organ meats. What happened?

They were starving.

Please fix title: Uses to Eat -> Used to Eat