NEWARK, N.J. (AP) — Gov. Chris Christie, who once famously called himself "the healthiest fat guy you've ever seen," disclosed Tuesday he had secretly undergone weight-loss surgery, a major new step by the potential Republican presidential contender to address both his health and a political vulnerability. The stakes are high for Christie, with medical professionals and campaign strategists alike suggesting there is no more serious barrier to his personal well-being and national ambitions than his weight.