Peanut butter and mayonnaise sandwiches were common not so long ago: during the Great Depression (1929 to roughly 1939). In fact, once Americans had acquired a taste for these high-calorie but cheap sandwiches, I suspect many households continued to serve such sandwiches to family members for many years after the end of the Great Depression. I wouldn’t be surprised if peanut butter and mayonnaise sandwiches are still being served today in many kitchens.
Note: Peanut butter and mayonnaise served on white bread contain roughly 400 calories, depending upon the brands of the peanut butter, mayonnaise, and bread involved. That isn’t excessive when you consider that the average woman needs to eat about 2000 calories per day and an average man needs 2500 calories to maintain their present weight. However, the exact recommendation varies, depending upon age, height, current weight, activity levels, metabolic health, and several other factors.
Newspapers in the 1930s suggested adding mayonnaise to “moisten” or “thin” peanut butter before adding bacon or shredded American cheese.
You can read more in the Gastro Obscura web site at https://www.atlasobscura.com/foods/peanut-butter-mayonnaise-sandwich as well as in an article by Chelsea Ritscheli in the Independent at https://ind.pn/2CRvfJl.
I think I will skip the sandwich, thank you.