Growing up in the 60's and 70's it was very common for a parent to say to a child, "Do NOT take more than your stomach will hold!" OR "There are starving kids in China!" (some parents said, "Africa"-- my parents preferred China for some reason.
Photograph with caption "Cafeteria Lines in Mess Hall
at Naval Barracks Area," U.S. Naval Ammunition
Depot, Hastings, Nebraska., 1944?
Taking a closer look we can see that the sign on the wall
that 'any wasting of food will be followed with disciplinary
action'. (can that advice even be comprehended by kids