President Trump gets stamina from the fact that he has "perfect genes," his Treasury secretary said Friday.

"He's got perfect genes," Steven Mnuchin said at a public interview with the publication Axios, when asked how Trump maintains his stamina with his notoriously lax diet and exercise regimes.

On receiving puzzled looks, Mnuchin repeated: "He's got perfect genes. He's got incredible energy, and he's unbelievably healthy."

The treasury secretary and former banker added that Trump no longer eats the fast food, especially McDonald's, that he was known for seeking out on the campaign trail. Instead, he enjoys the gourmet food prepared by the White House chef.

Later in the interview, when asked about the possibility of changing a piece of U.S. currency, Mnuchin jokingly responded, "I think we should look at putting President Trump on the $1,000 bill," referring to a denomination that does not exist.

Asked how Trump has changed on taking office, Mnuchin responded that he has taken on a greater sense of seriousness.

"This is not a formal, scheduled president who just has a bunch of people telling him what to do," Mnuchin explained, later saying that "he understands the seriousness of this job, and the responsibility."