As far as GW goes, I know that it forces your body to use stored fat instead of glycogen for energy, while also using up bad cholesterol too. AICAR comes into the equation because it can pretty much do the same thing without exercise, while enhancing the endurance effects.
Long-term research is still lacking on these peptides, so I don't know about the endurance effects in the long run. But I'd imagine that your body would eventually switch back to preferring stored sugar for energy after going off these compounds. However, the leaned-out effect that you would have achieved would still be there.