Former White House Doctor Concerned About Gov. Christie's Weight

Says "I'm a physician more than I'm a Democrat or Republican. And I'm worried about this man dying in office."

Washington (CNN) - Potential 2016 presidential candidate Chris Christie may be able to take the punch lines about his waistline. The popular New Jersey governor made light of his weight in an appearance on "The Late Show with David Letterman" Monday night.

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

But one medical expert on presidential health cautioned Christie's obesity is no laughing matter.

"I'm worried he may have a heart attack. I'm worried he may have a stroke," former White House physician Connie Mariano, M.D. said in an interview with CNN.