President Barack Obama has been in the Oval Office for about two and a half years, but the world's most stressful job has taken its toll. Obama turns 50 on Thursday, reminding us that he remains one of our youngest presidents -- only Theodore Roosevelt and John F. Kennedy were younger when they took office -- but he no longer radiates the youthful vigor that helped make him such a sensation in 2008. The endless grind of the presidency, particularly given the ceaseless attacks he has endured from a Republican party determined to make him a one term president, have deepened some wrinkles and led some grey hairs to sprout.

When you were sworn in, you looked like the guy from the Old Spice commercials. Now you look like Louis Gossett Sr," comedian Seth Meyers joked at the White House Correspondents' dinner. "If your hair gets any whiter, the Tea Party is going to endorse it," he added.

Take a look at photos of Obama's journey, from 2004 to present:

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Barack Obama, then a candidate for a Senate seat in Illinois and one of the keynote speakers of the 2004 Democratic National Convention, addresses delegates during the second night of the event at the FleetCenter in Boston, July 27, 2004. REUTERS
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U.S. Senator Barack Obama (D-Ill) waits to ask U.S. Secretary of State-designate Condoleezza Rice a question during her testimony before the U.S. Senate Foreign Relations Committee, during her confirmation hearing on Capitol Hill in Washington, January 18, 2005. REUTERS
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U.S. Senator Barack Obama (D-IL) attends a meeting with Israeli Foreign Minister Silvan Shalom in Tel Aviv January 10, 2006. Obama is on a two-day visit to the region. REUTERS
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Then U.S. Senator Barack Obama (D-Ill) (R) and former U.S. Senator Russell Feingold (D-WI) address questions from the media about ethics during a news conference on Capitol Hill in Washington January 8, 2007. REUTERS
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U.S. President George W. Bush walks with President-elect Barack Obama during a visit to the White House in Washington, November 10, 2008. REUTERS
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U.S. President Barack Obama holds hands with daughter Malia upon the family's return from Hawaii to the White House in Washington January 4, 2010. REUTERS
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U.S. President Barack Obama prepares to depart Andrews Air Force Base aboard Air Force One for a two-day trip to North Carolina, Florida and Puerto Rico, June 13, 2011. REUTERS
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