Christie takes fat jokes in stride (and with a donut)

(CNN) – His waistline could become a major factor of a potential 2016 presidential bid, but Chris Christie was all laughs Monday reflecting on his weight.

As he sat on David Letterman's couch - facing the comedian who often jabs fun at his weight - the New Jersey governor pulled a donut from his pocket and started nibbling away.

"I didn't know this was going to be this long," Christie joked.

Letterman and his fellow late-night hosts have long mocked Christie for his size, as well as for his pugnacious attitude at press conferences. But the Republican governor doesn't seem to take it personally.

"I only care if you're funny," he told Letterman Monday. "From my perspective, if the joke is funny, I laugh. If it's not funny, I don't laugh. But I've never felt like it was anything that bugged me all that much."

His family is constantly pressing him to lose weight, Christie said, though his doctors still tell him his health is "startlingly good."

"But I just turned 50," he added. "The doctor's now saying that things will start falling off me if I don't start getting things together. But up to this point, pretty good."

His cholesterol and blood sugar are normal, according to Christie.

"I'm basically the healthiest fat guy you've ever seen in your life," he joked.

In December, Christie pushed back at critics doubting his ability to lead because of his weight, calling it "ridiculous" to say he couldn't be president because of his size.

Though he admitted to ABC's Barbara Walters he's "more than a little" overweight, when asked if his size could hinder his ability to run for the White House he said "I don't know what the basis for that is."

"I've done this job pretty well, and I think people watched me for the last number of weeks in Hurricane Sandy doing 18 hour days and getting right back up the next day and still being just as effective in the job, so I don't really think that would be a problem," he said.

The county's largest president, William Howard Taft, weighed in at more than 300 pounds, and in a now-infamous anecdote, had the White House bathtub enlarged after being uncomfortable in a standard sized tub.

Asked by Letterman whether he'd decided on whether to make a bid for the White House, Christie said he was "nowhere near making that decision."

"I have to think anybody who tries to plan at politics that far in advance is crazy, because the world's changed, your life changes," he said, adding that in 2012 his entire family was against him running for the White House.