Christie's weight won't hurt him in an election. We have far more important things to worry about.
What will hurt him is his inexperience. Romney, Perry, and the others will be quick to compare him to Obama in that respect, and will use Christie's own statements that he doesn't feel ready and is not familiar enough with national issues.
His pragmatism will also hurt him. The best he could hope for is coming out of the primaries with independents questioning his readiness to lead and conservatives feeling angry that the establishment managed to retake control of the Republican party.
Once the country rejects Tea Party extremism in 2012 or, perhaps more likely, 2014, Christie will be in the perfect position to run. He knows it, and will not declare.