Still, Mr. Trump seems to come by his appetite for fast food genuinely.

While junk food has long been a staple of campaign trail life — Mitt Romney’s 2012 press corps coined the term “slunch” to refer to the unhealthy phenomenon of the “second lunch” — Mr. Trump’s reliance on high-calorie fare is driven more by a combination of speed, efficiency and, above all else, cleanliness.

Though he often orders from the Trump Grill when working out of Trump Tower in Manhattan, he eats fast food several times a week while on the road because “it’s quick,” as he told The Daily Mail last year while munching on Burger King on his Boeing 757-200.

Mr. Trump has even suggested doing away with state dinners, in a fit of cost and time savings. “We should be eating a hamburger on a conference table, and we should make better deals with China and others and forget the state dinners,” he said.

A man always prone to distraction and uninterested in small details, he has never approached food as anything other than a problem to be solved, quickly, as Gov. Chris Christie of New Jersey, an occasional dining partner, once told The Washington Examiner.

As the two men ate at Jean-Georges in Manhattan in 2002, Mr. Trump ordered briskly and imperiously from the head chef and owner, Mr. Christie recalled. “Jean-Georges, remember the appetizer you made for me last week when I was here?” Mr. Trump asked the owner. “We’ll take two of those. And remember that main course you made, the special thing you made for me? We’ll take two of those, too.”

Mr. Christie watched with confusion and a bit of awe, he recalled in the interview. Mr. Trump looked at him and said, “Don’t worry, you’ll love it.”

But Mr. Trump, who frets about germs and prizes cleanliness, also loves fast food because of its consistency and the promise, at least, of a basic level of hygiene.