How does diet and exercise affect blood lipid levels?

Diet and Exercise affect blood lipid levels in a good way. It all depends on your weight and genetics. If you diet and exercise you will start to lose weight and in turn, it will help your heart to become more healthy and unhealthy fat levels/ lipids to decrease helping to lower your blood pressure and improve your metabolism (Metabolism is the sum of the chemical reactions that take place within each cell of your body and that provide energy for vital processes and for synthesizing new organic material.)
I hope this helps :)

It is evolution, because we all have some of the same traits like eye color or shape or ears.