This paper makes for a good read summarizing all the FFA stuff.
For whatever reason, high serum FFA promotes insulin resistance, BUT.... and heres the important point, NO-ONE knows why this is currently. This is highlighted in the paper, at present, we have ONLY theories as to why it happens. If you ask me, its certainly nothing to do with "energy excess".
As I understand it, cells are ALWAYS in energy excess, they always have far more substrate floating around than what can actually be used. IF this was NOT true, then it would not be possible to fatally overdose on Dinitrophenol.
Something strange I have observed is that while taking Niacin, during the initial phase when my serum FFA drops, I actually feel VERY energetic.
But this is counter intuitive, if Serum FFA drops, I should in theory have less energy because I have less substrates for making energy. But this is complete opposite to what happens, when serum FFA drops, I feel MORE energetic, not less, thus that theory seems to be wrong. Lowering serum FFA increases insulin sensitivity aswell.
Further, 80 minutes after the niacin oral dose, when serum FFA shoots up and peaks, I actually start to feel tired and subdued!. Sometimes its so bad I have to lay down and take a nap! All the while I have MORE substrate available.........This is the paradox.
The only conclusion here is that high serum FFA reduces energy expenditure. THIS is also able to explain why we get insulin resistant during high serum FFA. Ofcourse one could argue that perhaps its the affect of Niacin acting on the GPR109A receptor. I also get very energetic in deep ketosis, which is associated with activation of this receptor.