Being president is stressful. Especially in the second term, when the demands of being the leader of the free world catch up with you.

President Obama acknowledged this at a fundraiser in Los Altos Hills, Calif., Wednesday, telling the crowd they could tell by his hair color what the past six years have been like.

"I’ve got so many friends, so many people who have supported me for so long.  As I look back, I realize how many of you have pictures of me with no gray hair," Obama said as the crowd laughed. "You’re chronicling the slow deterioration of Barack Obama."

Judge for yourself. Here's a photo of Obama campaigning in 2008 with Joe Biden.

(M. Spencer Green/AP)

And here's Obama leaving Seattle on Air Force One and heading to the San Francisco area Tuesday.

(AP Photo)