There are 2 types of fats, LDL and HDL. LDL is in the blood stream while HDL removes it.
HDL is more dense than LDL.
Doctors monitor LDL and HDL because there needs to be a balanced amount of both to stay healthy.
If you have more LDL and HDL, your bloodstream would have more cholesterol, which leads to Heart Disease and other complications.
When doctors are considered with cholesterol, they also have to keep track of saturated, unsaturated and trans fats.
The results of cholesterol tell you if you have high or low LDL and HDL. The patients look at normal levels and then their level and compare them both.
To change LDL and HDL levels you should.. Exercise, eat healthy, don't smoke, etc..
The intake of unsaturated, saturated and trans fat can be unhealthy if you intake too much. It can affect cholesterol levels to go up and that is not good.