I wouldn't call her overweight, per se. She needs toning, perhaps (and most people I know COULD use some toning, Yours Truly included).
I think that's why she (and most of the rest of 'em, too, because none of them truly appear to be grossly overweight, to me) came on the show. Perhaps in toning up, it can't hurt to lose a few pounds so as to tighten up what's left better?
I'm no Dr. Ian or Harvey, but that's the only conclusion I can come to.