Fatty liver is called steatosis, and fatty liver with liver inflammation is called or steatohepatitis.
Steatosis and steatohepatitis ["Fatty Liver"] can be caused by alcohol and other drugs and can also sometimes occur in patients with diabetes mellitus.
Steatohepatitis [Fatty Liver] that is NOT caused by alcohol is sometimes referred to as Non-Alcoholic Steatohepatitis or "NASH."
There's some info on this at
http://cpmcnet.columbia.edu/dept/gi/fatty.html
You should read that article. I think it will answer all of your questions.
Hope this helps.
An ALT of 72 is very mildly elevated. It may be of no clinical signifiance. With a level that low, I don't think a person could live long enough (100+ years) for that level to do significant damage to the liver. I wouldn't lose much sleep over this level, but be sure to follow through with your doctor.