Shurley it is effectively pulling mass to the centre?
Relative mass at the centre is increasing as the surface is venting, shedding mass. The body is losing total mass but from the surface only.
Increasingly over time, the body's mass is becoming relatively higher at the centre of the mass, as the surface sheds volatiles decreasing both mass and density at the surface.
Think of it as a spinning top whose external most edge is becoming a deepening layer of sponge, effectively pulling mass to the centre.
Or am i having a stroke?