I think the answer is clear: no. I also think the question deserved to be asked.
My own history with obesity is here, in all its gory glory. Fat stigma is an anathema to me, and I wish that we could ignore the issue entirely. We can’t. And that means that the fat of Christie’s will inevitably bleed over into the zone that perpetuates stigma and stereotypes. We have to find a way to judge Christie’s weight in the context of what the job of being presidential entails, and then, at the same time rigorously segregate it from any other type of judgment. If we can answer the question, then we ought to accept that answer and move on.
Christie himself has acknowledged that his weight raises the probability that he will acquire debilitating medical conditions, and has thus admitted to the public square a fact about his body that requires communal judgment. We should base our judgment on independent assessments performed by doctors. Should Christie run for president, he will submit himself to an examination, and when the results are known, they ought to be debated.