Nonalcoholic steatohepatitis (NASH) is liver inflammation caused by a buildup of fat in the liver. NASH is part of a group of liver diseases, known as nonalcoholic fatty liver disease, in which fat builds up in the liver and sometimes causes liver damage that gets worse over time (progressive liver damage).
Although the cause is not known, NASH seems to be related to certain other conditions, including obesity, high cholesterol and triglycerides, and diabetes. Treatment for NASH involves controlling those underlying diseases.
I copied the above from the net. NASH has only been given attention in the past 10 years. Obesity and diabetes are the most common causes of which I am aware. Addressing these often takes more willpower than medication.