I know Club Med offers several "wellness" options that include more active vacations.
I also heard that Canyon Ranch (the well known one all-inclusive-
fitness/spa in Arizona) is supposed to be opening a Miami branch soon.
Of course there's Rancho La Puerta in Baja ... pretty much right up there with Canyon Ranch as being well known.
I also think I read somewhere that one of the major cruise lines is doing a
fitness/weight loss cruise.
I'd hit up Google and see what you can find ... I know there are a lot of options out there.