"That's ridiculous," he responded.
Christie, who is widely mentioned as a possible presidential candidate as his national reputation has grown since the storm, had one health scare during his first term: an asthma attack on a humid summer morning in 2011 that diverted him from a scheduled press conference at a farm to a hospital. He addressed the press when he was discharged hours later, saying the heat, not his weight, contributed to the attack but vowing dietary modifications.
"I weigh too much because I eat too much," he said then.
He said Tuesday "there is a plan" for his weight.
"Whether it's successful or not," he said, "you'll all be able to notice."
Christie recited two of Letterman's fat jokes while appearing on CBS' "Late Show" on Monday night and told the comedian his laugh lines about his weight were funny "about 40 percent" of the time.