Dr. Connie Mariano, who served as White House physician from 1992 to 2001, told CNN she'd like to see Christie run for president in 2016 but that he needs to lose weight. She said she worries he could have a heart attack or stroke.
"I'm worried about this man dying in office," the doctor, who has a practice in Scottsdale, Ariz., told the network.
During a visit Wednesday to a shore town devastated by Superstorm Sandy, Christie was asked about the doctor's comments.
Unless Mariano gives him a physical exam and learns his family history, "she should shut up," the governor said.
His children heard the doctor's comments, Christie said, and his preteen son asked him if he was going to die.
"She's just another hack looking for her five minutes," Christie said.
Christie has never revealed his weight, but he has repeatedly said that keeping it in check has been a longtime struggle.
Christie joked about his girth during an appearance Monday on "The Late Show with David Letterman," pulling out a doughnut and saying his girth is "fair game" for comedians.
The next day, he spoke frankly about his efforts to lose weight and described himself as "remarkably healthy," but he also acknowledged his doctor "continues to warn me that my luck is going to run out relatively soon."
Christie has never released his medical records. He had one health scare during his first term, an asthma attack in the summer of 2011 that sent him to the hospital but did not require him to be admitted. He blamed it on the heat, not his weight.