Christie, whose persona as a notoriously outspoken Republican in the otherwise blue state of New Jersey, has long fought to control his weight.
A top Chris Christie aide tells ABC News that the governor kept his lap band surgery such a secret that even most of his top advisors didn't know he had the procedure.
Christie is in the midst of a run for reelection and reported this week raising $6.2 million in campaign cash. A successful reelection for a Republican in the Northeast would make him a stronger potential presidential hopeful. A slimmer figure might quiet questions about his health and his ability to compete in an exhaustive national campaign.
Christie underwent the surgery – a one-day out-patient procedure – on February 16 (the Saturday of President's Day weekend). He checked into the hospital under a pseudonym and told only his family and his chief of staff, who he told shortly before undergoing the surgery.
Christie's other top aides only found out about the surgery Monday.
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Another adviser to Christie told ABC News he has lost "more than 30 pounds -- so far."
The governor, at the White House Correspondent's Dinner 10 days ago, looked a bit smaller to people who talked with him. But his aides declined to talk about the weight-loss procedure at the time, apparently unaware that it had already taken place.
Christie opened up about his weight problem in a July 2012 interview with ABC News and stressed then that he was "trying" to lose weight, a battle he's waged for 30 years.
"It's something that's not easy. If it were easy, I'd already have it fixed," he said in July of 2012.
"Barbara I've had more diets and lost and gained back more weight than I'd care to count," he told ABC's Barbara Walters in December of 2012.
Christie told Walters it would be "ridiculous" for people to say his weight should keep him from the oval office. He pointed to the 18-hour days he put in when New Jersey was hit by Hurricane Sandy.
In July of 2012 Christie said he had never considered gastric bypass surgery because it's "too risky." Both gastric bypass and Lap Band surgery are variations of a bariatric surgery. Gastric bypass is a much more invasive procedure that involves surgically reducing the size of the stomach, among other things. Lap band is just like a band or belt that restricts how much the stomach can expand.
"I mean, see, listen, I think there's a fundamental misunderstanding among people regarding weight and regarding all those things that go into, to people being overweight," Christie said in an interview on "Nightline." "I think folks say — yeah, well he must just not be disciplined, you know, or he must not have willpower — that kind of thing. I guess the best analogy to make is some people drink too much. Some people take drugs. Some people eat too much. See, you can go live every day without drinking. You can live every day without taking drugs. You can't live every without eating."
Besides his weight, Christie said last year that he was healthy.
"My blood pressure's fine, my cholesterol is fine," Christie said. "I'm in good physical shape in terms of those indicators. But I have to lose weight and I get it."
Christie said there are two types of people who approach him about his weight: those who "really genuinely are concerned about me and want me to be around for a long time, and really care about me" and some of the people he sometimes encounters on his Twitter feed.
"There are some people who are just — you know, incredibly nasty and, and ugly and horrible," Christie said. "That's just the way it goes. I mean, you know, people have that kind of prejudice about them. I can't do anything about that."