Weight is a sensitive subject with Mr. Christie, 47, who seldom speaks publicly, even jokingly, about the subject. In an interview, he said he had struggled with his weight since he stopped playing organized sports at 18. In 1997, when he was serving as a county freeholder, he lost 40 pounds on a bet but gained it all back. The same thing happened after he dropped 50 pounds on the Atkins diet from 2002 to 2003.

He said he had become “numb” to fat jokes after so long.

“It’s one of the more difficult things I’ve had to deal with in my life,” he said. “But I don’t see how it’s relevant to my being governor. I was a really good U.S. attorney, and I was struggling with it for those seven years. It’s just part of who I am, unfortunately.”

Image Mr. Corzine, a fitness buff, said candidates often objected to depictions of themselves. Credit... Juan Arredondo for The New York Times

Despite the constant travel and take-out food of a political race, Mr. Christie said he had lost 25 pounds since June by working with a trainer three mornings a week.

“It’s not like I didn’t think it would come up in the campaign in some context,” he said. “But I think the governor has decided to overdo it. I think it’s silly, it’s stupid, and I don’t think anybody really cares about it.”

Mr. Christie declined to answer only one question on the topic: what his weight actually is. “No chance,” he said, with a laugh. He said the number would not cause concern about his health, but added, “I don’t think it’s anybody else’s business.”

Although significantly overweight politicians are increasingly rare these days, especially at the national level, several governors have very publicly tried to shed pounds, often unsuccessfully. Bill Richardson of New Mexico has told of trying the Atkins and liquid diets to little avail. Sonny Perdue of Georgia weighed nearly 230 pounds when he threw away a Snickers bar to start dieting in 2003. Edward G. Rendell of Pennsylvania has lost 48 pounds, but still carries 220 on a 5-foot-11-inch frame.