Hi you have posted your question in the hepatitis c community. Do you suspect you have hepatitis c?
Really fatty liver just by itself can cause liver irritation and a rise in ALT& AST. In fact fatty liver is an increasing health issue in the US.
The folks who said they have no clue are they liver specialists? In my non medical opinion as I am not a medical professional of any kind just a patient who was infected with hep c for many years and living with cirrhosis my thinking it is your fatty liver causing the elevated liver enzymes.
However, you will get a definitive answer from your gastroenterologist you will be seeing.
I personally don't think you need a liver biopsy your fibroscan is evidence of your lack of liver damage.
ALT and AST to not equate to liver damage it only shows something is harming your liver not the extent of damage. I have normal ALT and AST now that my hep c is cured but I still have liver cirrhosis.
My suggestion is try to get to a normal body weight check out a BMI calculator. But you best information will come from you physician.
Also you can try your question in the liver disorders community