Michelle Obama: Being president has taken a toll on her husband

First lady Michelle Obama said being president has taken a toll on her husband.

"I see the sadness and worry that's creasing his face," she told donors at a fundraising lunch in Pasadena, Calif., on Monday.

She's not the only one who's noticed. There was speculation earlier this year that President Obama was dyeing his hair. Observers noticed that two photos taken a few weeks apart had the president sporting different looks: the earlier one showing him with much more gray hair.

The first lady put that to rest, telling NBC's "Today Show" in February that the "lighting" accounted for the difference and joking that "if he had known he would be president, he would have started dying his hair, like, 10 years ago.”

She reiterated his work ethic supporters Monday, telling them the president was tireless when it came to his job.

"He reads every word, every memo, so he is better prepared than the people briefing him," she said, according to a White House pool report. "This man doesn't take a day off."

The first lady is on a two-day fundraising and campaign trip in California. On Tuesday she will speak at a Democratic National Committee breakfast in Oakland and lunch in San Francisco.

While in Pasadena she recounted her experiences on the campaign trail in 2008, recalling an event in Iowa where she was so comfortable talking to people, she took off her shoes.

"I was just standing barefoot in the grass, just talking to people," she said.

She acknowledged the next two years of campaigning would be hard. "It is not going to be easy, and it is going to be long," she said. "Now more than ever we need you help to finish what we started."

She's not the only member of the Obama family on a campaign swing. The president is hosting a fundraiser in Miami Monday evening and will hold another event in San Juan, Puerto Rico, on Tuesday night.

*Photo is courtesy of the White House and shows first lady Michelle Obama having coffee with the Queen Margrethe II of Denmark last week.