Inflammation or oxidative stress may trigger the progression from simple fatty liver (steatosis) to inflammatory non-alcoholic steatohepatitis (NASH).

“putting a bunch of fat in the liver is kind of like building the kindling for a fire so you build the fire and you don't light it then that person at some point they might not ever light that fire but all it takes after that all that kindling wood is put into place is some hit of inflammation or oxidative stress that suddenly lights that up on fire and in the literature that's called the two-hit hypothesis a fatty liver”