Going through the same thing from my husband AND my son.
I do think that my husband's worried about the personality change and confidence that comes with weight loss and my son is just plain scared of surgeries. It is a lot for them to take in, so I would suggest that you reassure her that no matter what happens or how more handsome you become, she will always be the one. This seems to comfort my husband when his insecurities take over and I comfort him. He is slowly coming around.
Hope that helps. Cheers,