Acetyl-L-carnitine, ALCAR or ALC, is an acetylated form of L-carnitine. It is naturally produced by the body, although it is often taken as a dietary supplement. ALCAR uses fat for fuel, breaks it down into fatty acids to your mitochondria, the mitochondria turn those fatty acids into ATP (energy) that powers your cells.
Though, if you're low on carnitine, fat can't get into the mitochondria, and you struggle to use it for fuel. But with plenty of carnitine, your fat metabolism works like a well-oiled machine.