It's arguably his most well-worn joke. President Obama loves to thank supporters who knew him when his hair was more pepper than salt.
His driver's license photo is the evidence, he joked at a polling booth this fall. Sometimes he blames his daughters. But don't worry, he reassures audiences, "Every gray hair is worth it."
As all presidents do, Obama has aged before our eyes — over six years shifting from a dark-haired politician drowning in his suit to a weathered president with the facial lines of an elder statesman. Or, perhaps, just a very tired one.
The transformation can be striking even for those who see him daily. A photo can capture red eyes and new wrinkles. A news conference with a younger leader, such as Italy's baby-faced Prime Minister Matteo Renzi, can draw a stark contrast.
Obama's worn visage recently prompted an expert on the subject (and there are experts on the subject) to call his wife over to the television to check it out. And it led an ecology professor in North Carolina to spend hours collecting photos of Obama for an only partially satirical scientific analysis.
Playing off the term for graying of the hair, he titled the work, "Yes We Canities! A quantitative analysis of the graying of Barack Obama's hair."
The graying of Obama has been a topic of discussion — and a favorite punch line — since his temples started to turn in 2009. But as Obama ends a year packed with turmoil, toil and political trouble, the temptation to blame the stress of a rough 2014 is strong, says the expert, S. Jay Olshansky, a public health professor at the University of Illinois at Chicago who has studied presidents and aging.
But it appears neither Russian President Vladimir Putin nor incoming Senate Majority Leader Mitch McConnell can claim direct responsibility for the changes that Olshansky and his wife spotted on TV. His research found no evidence that presidents show signs of accelerated aging while in office or die sooner than other men.
Presidents, including this one, appear to age at the same rate as the rest of us, he said. As evidence, he turns to technology that analyzes the wrinkles, spots, freckles, jowls and other insults to the face to estimate the approximate "face age." The technology is available at facemyage.com.
Obama's face age regularly averages below his 53 years, he says.
"It's just a misconception," Olshansky says of the idea that presidents age faster than others.
That false impression predates Obama. Almost every recent president has been observed as aging fast under the weight of a job with immeasurable pressure and a relentless schedule.
Bill Clinton's eight years saw his blond locks turn colorless. George W. Bush was often described as aging faster after Sept. 11 and the Iraq war. Ronald Reagan spent his two terms repeatedly denying that he dyed his perpetually dark waves — even as he departed office at 77 years old.
This president, too, has denied such charges, or at least his wife has for him. In 2011, First Lady Michelle Obama joked that that ship had sailed: "I think that if he had known he would be president, he would have started dying his hair, like, 10 years ago."
Obama's anti-aging practice appears to primarily involve his diet and exercise. Known to be a creature of habit, Obama sticks to a workout routine, complete with huffing and puffing as captured on cellphone video taken at a hotel gym this year, as well as what aides describe as a boring diet of fish, veggies and whole grains.
As a stress reliever, there is the golf — hours and hours of weekend golf — and regular card games with aides, a staple of any long flight on Air Force One.
When asked whether he was exhausted by the job, Obama claimed just the opposite.
"You know, I actually feel energized about the opportunities that we've got," he said on "Meet the Press" in September.
By comparison to some, he's still young, Obama noted recently. He mentioned that Cuban President Raul Castro, 83, called Obama "a young man" in their historic phone call to discuss reestablishing formal ties between the nations.
This fall, Matt Michel, an adjunct professor at the University of North Carolina Wilmington, looked at a picture of Obama and got an idea for a new research paper for his online journal, Proceedings of the Natural Institute of Science.
Michel collected and cropped dozens of photos of Obama's hair, assembled them in chronological order, plugged them into Photoshop and quantified the gray value. Michel's result: As of October, Obama had gotten 136% grayer.
And odds are that his hair will indeed, as Obama joked in 2012, reach "100% MFH" (Morgan Freeman Hair) by 2016, according to the article.
Even in MFH territory, Obama will likely be within normal range, Olshansky notes, stressing that when we note that a president suddenly looks old, what we're probably observing is actually a harder truth: We look old, too.
"It's a reflection on us. It is a direct reflection of the normal process of aging that we all experience and especially that we all experience right at that phase in our life," he said. "Those of us that are in that our 50s and 60s — I'm sorry. We're all aging; he's just part of the crowd."