Why is it easier for your body to break down unsaturated fats than saturated fats?

In terms of diet, unsaturated fatty acids are considered 'better' because they have a bend in their chains that makes them difficult to stack in the cell membranes. To correct this, the cells put a molecule of cholesterol in the cell membrane as a "shim" to make the lipid bilayer more stable. Because unsaturated fatty acids cause the cells to consume and utilize more cholesterol, they help to reduce the amount of circulating cholesterol which then reduces the risks for Heart disease.