That's pretty cool! You can also, instead of just lowering the hue and saturation, select the skin color. Then put it on a new layer and invert it. Set the blending mode to hue or color and lower the opacity. That makes the skin color neutral.
Good technique to use for portraits, fitness shots or anything you want to give a more stark appearance. One thing that you might want to mention (or be careful of) is doing this with a model wearing dark clothes on a dark background. The finished product looks almost like the model is chopped in half.