Both the albumen (the egg whites) and the yolks contain protein. However, the yolks also contain fats, which the whites do not. A delicious omelette can be easily made form just the whites. Cook it as you would any omellete...
Here's one we often do:
Three egg whites
Three asparagus spears, blanched and cut into 1-inch sections
1 tablespoon chives, chopped
Olive oil
Salt
Ground pepper
Directions:
Heat a tiny amount of oil in a non-stick omelet pan. Beat the egg whites with a fork and add the chives, salt and ground pepper.
In a separate pan, toss asparagus in some oil until heated through, then season with salt and ground pepper. Set aside and keep warm. Pour the egg white into the oiled omelet pan and, with a fork, quickly draw the edges to the center, so the omelet cooks evenly.
When cooked but still creamy place the asparagus in the center and leave on the heat for a second longer. With a fork fold the omelet towards the far lip of the pan, giving the pan a light tap to loosen the omelet. Slide out onto a warm plate.