Dave Feldman, researcher, says they can't be separated. He is about to run a N=1 experiment where a random number generator will put forth an LDL level for him to achieve. Then he will have ten days to achieve this level. He will do it with diet changes. He wants to show that LDL can be changed widely and rapidly with simply diet changes and these changes are predictable and repeatable. LDL can vary widely over a relative short period of time. 

Six minutes long describing the challenge.

https://www.youtube.com/watch?v=UJVXim5YCOk

His lipid energy model:  https://www.youtube.com/watch?v=AkzxESsTJyM