From what I can tell, here's a general idea of what was done in no particular order:
1. Digital Liposuction of the belly - Achieved by using the liquify filter in Photoshop
2. Desaturated the whole picture and made the background black and white
3. Desaturated the model selectively probably down to 25% saturation
4. Burned the hell out of the edges and selectively dodged the model
5. Cloned away stray hairs, unwanted shadows on the face/body
6. Dodged and burned the skin (mainly arms) to give it a smooth shiny even tone and a more 3D look
Basically, to get this, you gotta be good at dodging, burning, layer masks, cloning, desaturating, and liquifying
