A noticeably grayer and thinner President Obama turns 49 on Wednesday, and he has been joking for days about how the years are taking their toll.

Last week at a submarine sandwich shop in New Jersey, Obama joked with reporters that he could not order the full sub because he has gotten older.

"I can’t eat a 12-inch these days, now that I’m 49," Obama said.

White House press secretary Robert Gibbs acknowledged Tuesday that the job does take its toll on whomever is president.

"I can't imagine that the weight of the job doesn't take its toll physically and mentally on anybody that does it," Gibbs said.

The president is planning to spend his birthday in Chicago, having dinner with old friends, while First Lady Michelle Obama is visiting Spain.

Gibbs said that Obama "knew what he was getting himself into" when he decided to run for president, but he is still "enjoying the job."

"It just requires him to get more frequent haircuts," Gibbs joked.