They're short and wide, the top of their hips and their waist is very low relative to the top of their legs, their shoulders are unrealistically broad. The male body is closer to realism yet way off, while the female body ignores all skeletal differences between men and women and simply tries (poorly) to slap boobs on a slightly skinnier male body--it makes the body thinner by deleting the inside seam.
Would be nice if a pixel artist could re-do the base images to keep the original design of the looks while making the base shape of the bodies look more like humans. I'd like something like this to be incorporated as a default mod in the base openxcom.