Basically, a soft body squashes and stretches as it moves:
But Buddah-Belly the Orc needs to be super squetchy, and his tumescent tummy needs to be even more squetchy than the rest of him. In addition, his ponderous paunch should exhibit secondary motion. That is, it should lag behind his body. In short, jiggle-physics.
When building these characters, I just slap a rig I've previously made on them (the rig is an armature you use to pose the character. Those circles sticking out of his face and stomach are handles to let me use the rig.) It works terribly, but the players won't see the 3D model. Unless they come to this blog.
Since I need to manipulate his gargantuan gut independantly of the rest of him though, I had to add an additional belly-bone to the rig.
Accordingly, Our Hero wobbles while he works. It's not super-noticable, given the intentionally low frame-rate, but it adds a little, ahem, weight to his walk.