There also seems to be a correlation between various fat consumption and satiety. Polyunsaturated fats do not strigger the same processes as saturated fats in the mitochondria. Basically saturated fats signal for more fat to stay in the blood and trigger satiety. PUFA's do not work the same way, they keep accepting theses fatty acids into the cell allowing it to enlarge. Therefore, contributing to obesity.

Comparing correlation, we see a big rise in obesity around the same time that we started demonizing saturated fat in america and promoting PUFA use.