Critser said that in some places or subcultures, there was a tacit endorsement of being overweight. (In some places there was overt endorsement.) Chairs in restaurants got bigger, especially in fast food restaurants. Clothing sizes changed to accommodate a larger body for the same measurement. And a political correctness emerged (in the 1980s?) - where it was important not to shame people, especially children, for being overweight.
This last point might be illustrated by a theme song used by the President's Council on Physical Fitness, under JFK in the early 1960s. Its refrain was, "Go, You Chicken Fat, Go!" Also, according to Critser, in the 1970s the Council used an advertisement showing a giant marshmallow and declared, "Hey kid! If you see yourself in this picture, you need help!"
Here's the "Go You Chicken Fat Go!" song.1 This is not satire. I remember having to do those President's Council push-ups in the hot sun in the parking lot next to my grade school.
"Give that chicken fat back to the chicken and don't be chicken again .... Noooo, don't be chicken again."