McDonald's, after going through its first annual decline in sales in 30 years, goosed its market a bit this month by selling its breakfast offerings all day, which is expected to add one percent in sales over the next year.

So that's why. But what about the why not? Why did McDonald's breakfast foods only sell at breakfast, anyway? In fact, why do we only eat what we consider "breakfast food"—omelettes, pancakes, bacon, etc.—only at breakfast? Because someone wanted to sell us something, of course.

If you work in journalism, or read it a lot at least, you probably know about the endless pitches from publicists touting industry- or company-sponsored polling designed to provide a quick little hit of content. The man who truly created this approach was named Edward Bernays, the nephew of Sigmund Freud and the father of public relations more generally.

In 1922, the Beech-Nut company hired Bernays to try and sell one of its products: bacon. "We made a research," Bernays said later, "and found out that the American public ate a very light breakfast of coffee, maybe a roll, and orange juice."

This hadn't always been the case. As historian Abigail Carroll told Gastropod, breakfast used to be a convenience of leftovers: "You were having a pretty spontaneous, ad-hoc, often cold, collation of often leftovers or what was pretty easy to get." As people got richer, they added meat to it, but it tended to be regional—fish and eel on the coast, ham in Virginia, scrapple in Philadelphia. As the fat of the land grew, so did breakfast. "It wasn't as though meat replaced what was eaten before, it was added on. There was kind of a snowballing effect," she says.

During and after the Civil War, though, America suddenly had to combat a "growing dyspepsia epidemic"—chronic digestion problems due to high-protein diets. Doctors recommended cereal, one of the original "health foods," according to Tory Avery of PBS's The History Kitchen

Then another change occurred. In the late 19th and early 20th centuries, American hotels tried to appeal to middle class and European travelers with a "Continental breakfast." Slate's L.V. Anderson explains:

Americans traditionally ate large quantities of hearty, fried fare for breakfast, like pancakes, eggs, and meat—holdovers of the agrarian lifestyle. European visitors to America were appalled by such greasy abundance, preferring lighter items like fruit, bread, and pastries. Hotels began offering such continental foodstuffs to appeal both to Europeans and to health-conscious Americans.

Enter Bernays. He and Beech-Nut approached a physician who told them he would recommend a "heavy" breakfast—basically, bacon and eggs—over light items, again for health reasons. A heavier breakfast would, according to this doctor, replenish energy lost overnight. Bernays asked him to write about 5,000 of his colleagues and ask their opinion on the matter. Nearly all of them, Bernays said, concluded that a heavy breakfast was "better for the health of the American people."

Bernays approached the Medical Review of Reviews to publish the study—the same publication that he had edited as his first real job out of college and where he learned his first lessons in public relations. In August and September 1922, newspapers throughout the country dutifully reported on the study. “GOOD BREAKFAST IF BRAIN WORKER, PHYSICIANS SAY,” headlined the Chicago Tribune, using a much more awesome term for what we'd now call white-collar workers. "Brain workers and persons in sedentary occupations should eat a substantial breakfast, but a light lunch," it quoted one Dr. J.H. Riffe of Covington, Kentucky as saying, who recommended that breakfast should consist of "fruit, cereals, bacon, eggs, toast—or as we of the south prefer, hot biscuits."

The Los Angeles Times editorialized with a hot take, ENTER THE BIG BREAKFAST:

We were in dire peril of falling for the finicky French roll and chocolate, the virginal [Ed. note: !!!] English tea and marmalade, the slice of fruit and swallow of vermouth of the Mediterranean.

Not so breakfasted the men who hewed a new civilization from the rocks of the Western continent…. Ham, eggs, bacon, cornmeal, buckwheat cakes, maple syrup, codfish balls, coffee in great mugs, hot biscuits, butter without stint or limit, hash, fried potatoes, apple pie, farm-made cream cheese, bowls of warm, frothy milk—on the strength of such breakfasts as these the young republic grew to world overlordship.

And then there came a period when the good, old, American breakfast suffered a temporary eclipse. It came to be a fad to start the day with a nibble instead of with real eats. About that time Woodrow Wilson was elected president.

It's a style of high judgmental dudgeon about how one breakfasts that, apparently, never gets old.

Bernays won bacon's inclusion in the day's first meal, though the fatty food would have to be rescued again as health trends turned against it; this time, the far more straightforward and relatively unassailable PR approach of "yeah but bacon tastes good," led by that fixture of my childhood, Hardee's Frisco burger, got Americans eating it again, on anything, all day. (This week's news that bacon can cause cancer may necessitate a third attempt to resuscitate the food.)

So you can thank Sigmund Freud's nephew for allocating bacon—and eggs, and maple syrup—to just breakfast. Eighty years later, the nation's largest fast-food chain may finally be breaking that trend.